Yeah, it is something that does damage games, for me. My first 3D-rendered rpg was Morrowind. All this freedom, all these physics-based obstacles. Then, I see people get over-enthousiastic about "role-playing games" like Kotor, which to me feels like a clunky linear dungeon-crawler, even when set outdoor. I've really been spoiled too much by the Elder Scrolls approach (and Far Cry's, if I remember well) to not be taken aback by the invisible walls and impassable two-inches-high fences of so many free-roaming open RPGs or shooters.

In-game purchases for a singleplayer game. I bought the game, I don't want to see advertisements on my main menu reminding me that I am missing additional content.

How about the combination of these two things:
1. Skill system that gives you finite skill points and doesn't allow respecs
2. Game balance changes drastically, making the abilities you used early game utterly useless late game, essentially invalidating your build

Or, alternatively:
2. Part of the game makes certain types of abilities useless. If you focused on those abilities, you are basically stuck when you reach that point.

(Of note, I don't like skill systems like the one I described in point 1 in general.)

Also, counter-intuitive mechanics that punish players long-term for expecting things to work in a sensible manner. For example, in the Famicom/NES version of Dragon Quest/Warrior 3, using Vitality or Intelligence seeds will actually hurt your HP/MP growth. The thing is, you only gain HP/MP when your Vitality/Intelligence increases at level up, so increasing those stats another way will reduce the amount of HP/MP you are able to gain. There is an item that directly boosts max HP, but no comparable item for max MP. (The remakes fixed this issue; now using the seed will give you more HP/MP on your next level up.)

What kind of invisible walls specifically, and what approaches can you recommend as hard working good game design alternatives? If possible could you mention a few games that illustrate the lazy and bad game design, and some which show what you consider to be a superior alternative? I've got some of my own ideas but I'm curious how other people see these things also.

Well, with 'invisible walls' I mean limitation where you can go, although according to graphics and game dynamics you should be able to go there. The latest example where I hit such a wall was Hard Reset. There are numerous examples where you can see a path / some goodies behind a wall of crates and although you should be able to jump over that wall (and you can jump over other, similar walls), you can't because your character hits an invisible barrier in mid-jump. There are other games where that is much more frequently the case. If you want examples, just look up 'bad game design invisible walls' on Youtube. There are lots of rants about that.

The better alternative would be: just don't do it! Make all walls visible. If a player isn't supposed to go somewhere, place an in-game obstacle there. Walls, steep mountains or even forcefields or magic barriers, depending on your setting. All are valid options of limiting the playing field. But don't ever use invisible walls out of thin air without any ingame reason.

Yeah, this annoys me too. Especially in urban settings where the path is linear and you have lots of side streets that look like you should be able to go down them but you can't.

One way of getting around this which I think is quite good is actually to have a decent map that shows where is walkable (as you discover it) and that way you can at least check the map to see if you can go somewhere before spending twenty minutes trying to figure out how to get to somewhere you're not actually able to.

But I agree, in general it's better to actually physically block the player so there's no doubt whether an area is accessible or not.

There's also level cap. Which feels sometimes awkward when you're halfway through the game and cannot level up anymore. But, again, there is level cap and level cap.

Some games are sufficiently unRPGish for this to not matter. Mad Max lets you level up you character to the max very early, but, hey, who cares, it's an action game. These stats don't matter all that much. Some genuine RPGs have to prevent you from grinding your way to godhood (and to then whine about how trivial the rest becomes). Okay.

But when some games limit your levelling possibilities before you can even max your stats or fill up one branch of abilities (by limiting the levelling opportunities, or the ressources required for it), it became bad bad design. It forces you to metagame your level plan from the start, in order to be sure to unlock this or that ability. It forces you to play in accordance to a pre-established path, and to pop out of the game at every step to make sure you're still on the right predecided tracks. And this ruins the game.

The Elder Scrolls sometimes do it, to some degree, with its primary and secondary stats. Don't level up this or that stat too soon, you'll lose the opportunities to level up that or this. But the most broken system, in that regard, is the Smugglers V game. Which is one of the very few games I've regretted buying. And which, although looking like an open game, punishes you for having wasted one of the limited level up on a secondary development branch. Wanted to max out or unlock this ability ? Well, better restart and focus on it, because, surprise, now you won't level up ever again, even if you continue playing for ten years...

More often than not, I welcome cap-removing mods.

This is definitely a pet peeve of mine. Having to actually look at a guide at character creation to make sure you don't mess up by putting points into skills that don't complement each other well and you end up not using one of them really takes some of the fun out of a game.
Even worse is if it's possible to make it half way through the game before realising you've seriously nerfed your character by not planning them out properly.
I'd much rather a system where if you get bored of being a mage or a fighter have way through the game you can (with some effort maybe) change your path and still be just as powerful as if you'd started that way all along.

It's one of the reasons I really enjoy roguelikes, because you get to try lots of different styles of play and see what works, what you enjoy and how best to play different characters / classes.

Allow me to reiterate the unskipable cut scenes, and badly placed save/autosave checkpoints.
Mass Effect 1, the planet you get Liara, the damned krogan on top of the elevator. I always tried to do that planet first so I'd have Liara around for most of the game, which also meant I did not have as many abilities around (like immunity or whatnot) to help prevent or cause damage. That damned Krogan killed me so many times, and the autosave as at the beginnin of the elevator ride, and you had to have a dialog with Liara, and then a short one with the krogan... over and over again untill you beat him.

Another is not being able to rebind keys. Modern games are a little better with it, but it is especially noticable in old games.
They want one hand on your mouse, and then your other hand is expected to hotkey buttons both on the left and right of your keyboard at the same time? Just because the letter on the key is the first or second letter of the ability? screw that.

In a similar vein as the last one, the "One button does all" mechanic. Its a hallmark of consoles, seeing as there are so few buttons to work with, but its horrible when the game is (badly) ported to the PC and they leave that in.

Again with the Mass Effect series, this time 3: why on earth would you make one button be "use/activate" "run" and "take cover" at the same time?
Oh, I just need to activate this console here. Nope I'm taking cover. Hey, my teammate needs revived, guess I'll just repeatedly take cover beside his dying body!
And my favorite: I'm dying and need to flee! Hey there's cover remotely near my path, so I'll just take cover here in stead of running, so the guys with guns shooting me from behind have a stationary target to hit!

The only way to fix it in this particular game is to get what basically amounts to a cheat program, and then reset the bindings, but to do so you need to know how to do bindings in Unreal engine. Annoying is a good word for it.

There is actually a nice solution for this issue that doesn't involve removing such a cap:

Make it trivial to respec your character.

By "trivial", I mean, at least, having a place (in a town, for example) that's always accessible where you can respec your character. Even better would be to allow it to be done anytime you aren't in battle.

The original Paper Mario does this rather nicely with its handling of BP (Badge Points); you can get the BP spent on a badge by simply going into the menu and un-equipping it. For the permanent HP/FP/BP boosts at level up, someone in town (Chet Rippo) can somewhat tweak it for a fee, and if you focus on BP, there are badges (HP/FP Plus) that allow you to convert BP to HP/MP, making BP heavy set-ups a nice option.

When playing Avadon 2, I really loved the fact that there was a cheat that would let you respec your character anytime (though I would recommend not using it during battle if you don't want things to get too silly).

One of the reasons Final Fantasy 5 is my favorite game in that series is that you can change a character from fighter to mage (or vice versa) and the character is immediately competent in the new role. For example, a character who has never been a White Mage can still use all the White Magic you've bought if she is actually in the white mage job. (The reason one would want to level up the class is to be able to use those spells in *other* classes.)

Also, I note that FF games (from 5 onward) typically solve this issue by making skill acquisition separate from leveling up; each battle gives you AP (in addition to XP and gill) which is used to learn skills, and leaning a skill does not increase the cost of learning others, and there's no limit on how many you can learn (though there sometimes is on how many you can have active at once).

Yeah, Final Fantasy (5 in particular) is a good example of a method that works. Having the two separate XP pools means you can switch classes and with a little grinding be as good as your previous class.
Though it does generally mean that your power is limited (which may not be a bad thing) as your levelling and stats are independent of your class.

I really like how Fire Emblem Awakening (and presumably the newer ones which I have yet to play) manages classes and levelling up. Although level ups are random (and can range from really great to awful) and can give you stats not particularly useful to your current class you can basically level indefinitely if you really want to as you can reset your level (I think you lose some stats if I remember correctly, but you can more than make up for it by regaining your 20 levels again).

Actually, in Final Fantasy 5, stats (other than HP/MP) are actually dependent on your class (and sometimes your secondary ability), but not your level. A level 99 Knight will have the same Strength, Agility, Stamina, and Magic Power as a level 1 Knight.

On the other hand, Level does play a role in battle calculations, but one fun thing is that there are abilities to manipulate that.

I did know that but had forgotten as I haven't played in ages. I was actually quite surprised last time I played to realise that my stats didn't improve (I never noticed as my equipment generally improved as well, and I never stayed as one class for two long unless it was one I was looking to master, and I tend to save that for later in the game when AP is easier to come by), but it makes a certain amount of sense I suppose and means you don't end up with unsuitable characters, which is possible in other FF games like FF Tactics Advance where you gain stats based on your current class when you level up (I think). On one hand this means you can build a hard hitting and tough mage (who probably won't be brilliant at magic) if you want to by levelling as a knight or something first, but it also means if you want to get a specific skill for a build your working on then you might gain stats that aren't great for you.

Ah, ok. Yeah, there are different categories, some of which are difficult to avoid without it having other problems, but I think I understand what you mean now. One game that annoyed me like that was Lord of the Rings War in the North. There is the game world itself, and then they outlay it with this invisible path you must walk within and are bound to, sometimes where there are natural barriers and other times just an invisible line in the sand to which there would otherwise be no consequence of crossing. It breaks immersion and IMHO is often used as a way of avoiding more complex collision detection. When it is done like that I brand it as a form of "consolitis" as the games have this distinct "I was made for a console and ported to PC cheaply." feel to them.

The problem is more complex when it is on the scale of the edges of a game map/level though. At that level I find that bodies of water and mountains are the most believable and least immersion breaking, but if every game map was surrounded by an impenetrable body of water and/or mountain then that would become the new eye-roller too. No easy perfect solution to that particular problem unfortunately other than every game implementing full planet sized worlds in which you can travel in every direction until you wrap around the planet back to where you were. That would go way beyond both the scope and scale of most games, the development team's engineering capabilities and budget, and/or beyond what modern hardware could easily handle just to avoid a small albeit annoying edge-of-the-map problem that almost every game ultimately has. The same is true in RTS games and other genres too, not just RPG/FPP/TPP ones. For those that have went to planet sized worlds to handle the problem, most of them the planets are extremely small with a highly noticeable curvature as a result which itself has its own issues in terms of believability.

The finer problem you describe where things are off-limits within a level is solvable easily enough if the developer cares to put that much more attention to detail and remove unnecessary limitations in their engine and game, while the edge-of-map problem is more difficult. The most promising solutions I've seen floated for the latter problem are full planet sized game worlds where perhaps the planet itself is procedurally generated to begin with, then the developers can customize and build things on the surface from there, custom landscaping specific areas, while the rest of the planet resorts to the procedural algorithms. I'm not sure but Star Citizen appears that it might work along these lines at the planet scale. Mind you the problem then becomes whether the game should have planet scale wandering or not, as that could change the entire dynamic of the game.

I think I'm often annoyed just as much by an impenetrable mountain around the edge of a map or body of water, as I am with an invisible wall in such edge-of-map situations in games. It's kind of a no-win situation for game development quite often I think, however some games handle it ok. Far Cry for example solved it simply by existing on tropical islands in the middle of the ocean, and some attack helicopters and similar that try to keep you from trying to become Christopher Columbus. :) If every game did that, it would get tired real quick though.