Defender's Quest!

It is well balanced, has a charming story, some RPG-elements and is overall fun.

Lifthrasil said it.

I'll second Defender's Quest.

I've played the first Kingdom Rush game and it's pretty solid as well. The sequels/prequel? are likely similar.
This game spawned a number of clones such as Royal Defense (a much inferior copy).

Anomaly Defense is decent too. Not as unique as the Tower Offense games, but it's pretty solid.

The only other one I recall playing (on GoG) is Pixeljunk Monsters and it didn't grab me at all.

I'll third Defender's Quest, spent many hours lost in that game, one of the most well polished in the genre.

Wow, surprised to see so much support for a single title I've overlooked. I checked out the forums and it looks like the developer's been active with the community and they've gone the extra mile to please individual players.. that is really impressive. That kind of thing earns my respect.

Alright folks, I'm definitely checking out Defender's Quest.

(Secretly I wish we had something like the Gemcraft series here)

I cast my vote for Defender's Quest as well. Got it in a bundle for Vapor time ago and turned up to be the best of that bundle.

Good luck down there!

Of those on gog I've only played Kingdom Rush, and I thought it was excellent. So, that one then? It's for free on Kongregate if you want to check out the gameplay, but just note that it's a much poorer version than the gog and steam versions.

defender's quest and Kingdom Rush are teh best.

Defenders Quest is definitely fun, but I prefer Kingdom Rush. I've played the first two on Android, I presume the PC versions aren't really any different, and the third one is probably of similar quality.

All Kingdom Rush games are also very good.

Here's a related question:

Are there any other Tower Defense games on GoG besides?
Defender's Quest
Kingdom Rush
Kingdom Rush: Frontiers
Kingdom Rush: Origins
Anomaly Defense
Pixeljunk Monsters

I know Van Helsing has a tower defense mini-game, but that hardly counts.

The mini game was actually made into a full fledged game:
Deathtrap

It does not contain the level editor though.

Aegis Defenders is a action platform tower defense game.

Yup, Defender's Quest have a lot of fun, also a NewGame+ mode with some new stuff ^_^

I'm not a big tower defense guy but I remember having a TON of fun with Sang Froid. I bought it on a whim because I loved the setting, plot and mix of planning and RPG. I mean come on, lumberjack brothers upgrading their skills and gear in the Canadian wilderness while fighting off werewolves, using a variety of weapons and traps??? Find THAT in any other game ;)

The game ended up being a ton of fun with some simple but solid action gaming and planning interjected into the initially trap laying. I went so far as to solve it as the "easy" brother" - (the big bulky guy) and I always regret not going back and doing it all over again as the other one. Even when I lost a map, I loved going back over my "plan" figuring out where I would be best served laying down traps, slowing enemies and figuring out where I should go fight first and where I should try to stall the baddies long enough to get my mission done.

Plus it's just criminal that the game is free - stupidly fun game and totally worth the time to download it and give it a shot.