I think a good leveling system can make or break an RPG or everything else with an EXP system. I really like being able to spend 10+ minutes on level up screens or just looking forward to being able to spend these next few points once I get a bit more EXP. Games, on the other hand, where a level up just means getting a fixed amount of stat points and specific skills at specific levels make a level up utterly boring.
So I'd just like to collect unique, fun and/or complex leveling systems of different games in this thread. Whether it's on PC or not shouldn't matter.

I think there are a lot of games to mention, but I'll just start with two:

Sacred 1/2:
The fact that unlike usually giving to many points into your skills is extremely detrimental and that you can just socket all your skill points(except the first) is something I liked, though I never quite understood this till Sacred 2. The abilities are also made well, getting to choose between multiple viable ones at specific levels.

Neverwinter Nights 1/2
The ability to combine up to 3 classes, some of which have requirements for choosing, the difference in Talents, Skills, Spells, Class specific abilities and more made every level up and the whole planning progress really fun. Imho the best level up system I remember. Though other D&D based ones I never played might have been similar/better.

Just finished Final Fantasy 8, the Guardian Force system was interesting. You still level up with exp, but you actually shouldn't until you obtain the right Guardian Forces with bonuses to leveling up. What magic and the amount you have converts into higher stats. What combination you assign your guardian forces with different abilities to different characters was also complicated.

Oh definitely Serpent in the Staglands. I was totally perplexed when I gained my first level, which I found curiously refreshing. It's a really cool game, though the balancing was messed up for a while until the patches started to roll out.

Might and Magic VI has interesting approach. You gain HP/SP on level up and few skill points. All skills also have 3 tiers of mastery. Beside that, you can increase primary stats and resistances throughout game. Add on top of that diablo-like loot system. Oh, and there is no level cap. You become significantly weaker when you level up in FF 8 because of disastrous level scaling. Junction also means drawing hundreds of spells and never-ever using them, except maybe Aura. That game was broken on so many levels, it was just bad.

This is incorrect. I was completely overpowered and crushed everything except Omega leveling up and drawing magic normally. Enemies do level up and have better spells, but you have guardian forces and magic junctions and massive stat bonuses, they mostly don't get those bonuses.

theres always teh system from elder scrolls morrowind that one was different in how it worked you had to be careful in how you were gaining your exp for level up

Agreed -- It's still a decent game overall, but some of the game mechanics in FF8 were pretty bad and tedious.

Wizardry 8 has an interesting hybrid system. When you get enough experience points, you can level up, gaining stat points to distribute, a spell pick to choose, and then some skill points.

However, that's not all of Wizardry 8's growth system. If you use a skill enough, it will improve on its own. In other words, you do get some improvement between level-ups. It's especially fun if you are using a Bishop, who gets all of the magic skills but doesn't get extra level up skill points, so you need to use your spells constantly to improve them.

The SaGa series (console/handheld only, with many games being Japan only) also has some complex systems, which vary significantly. Here is how SaGa 1 (also known as Final Fantasy 1) handles character growth (note that, like most SaGa games, there are no levels or experience points):

Humans gain stats by using consumable items buyable from the store. Many games have items that provide permanent stat boosts; this game goes further and makes it the *only* way for humans to gain stats.

Espers (Mutants in English version) gain stats and special abilities randomly after battle. Or, rather, their stat gains are goverened *solely* by the game's RNG. This is an important distinction, as the game has one of the worst RNGs I have encountered in any game. Sometimes it's necessary to use tricks (like moving the character to a different party slot or selecting New Game and soft-resetting during the intro) just to get fresh randomness; otherwise you can have problems with an important stat (such as HP) not increasing. Also, the model of Game Boy being used matters; a Game Boy Advance will give different random numbers than an early Game Boy.

Monsters change form when eating meat, getting an entirely new set of stats and abilities each time. This is not random at all, but is determined by a table. Note that there is the risk of changing into a weaker form later on, so be careful.

Vagrant Story doesn't have levels. You craft better weapons, armor and shields and increase your weapons elemental affinity to different types of enemies. One of my favorite rpg's.

Not oddly for Squaresoft they actually tell you to do the complete opposite in the game, increase your enemy type affinity and not elemental affinity which leaves you massively underpowered.

I thought the Sacred games were cool for the level up system too. Path of Exile on steam is another game of the same genre and it really has a pretty interesting and complex way of building characters also.

I'm not a huge fan of the game itself but I LOVE the level up in Dungeon Siege. It auto levels up whatever you use the most; brilliant!

Okay so it's brilliant for lazy people like me, but doesn't our vote count? :P

Every vote counts. Everyone should vote. Ok, so maybe it don't matter who you vote for in the end anyways.

BTW you are obviously a Sacred fan; have you ever figured out a fix for the Sacred 1 FPS drop when zoomed out?

Honestly it's been about 10 or 12 years since I played the first one. I don't really remember such a bug, I'm sure it would have drove me nuts. Or maybe I became more anal about the fps later on I don't know. lol I was thinking of picking it up again on here as well as the second one. I have the discs for part 2 (well without the expansion) still but not the first anymore or I'd fire it up and see if I can replicate it.

I do really like the second one a lot yeah. I've played it more. Although I think some of the classes in the first game were better, or more fun to play then some of them in the second game.