Defender's Quest. I can't go back to Kingdom Rush after that.

Not exactly "Tower" Defense (rather an action trap defense), but Orcs Must Die 2 is fun if you have a friend to coop with.
Go Home Dinosaurs was fun but short, should wait for a sale. Easy 100p if you're into achievements.

Also, you can try the Gemcraft games (I finished only Chapter 0 and 1) and Cursed Treasure, they are nice free TDs (you don't need the premium stuff for the Gemcrafts usually).

http://www.kongregate.com/de/games/gameinabottle/gemcraft
http://www.kongregate.com/games/IriySoft/cursed-treasure-dont-touch-my-gems

I could also recommend some games given by other people, but as wished I restrain on those I completed.

Definitely go for Defender's Quest. That's a great game.

I can also highly recommend Sang Froid - Tales of Werewolves. That is a very unique game that mixes combat with tower defense. You don't need lightning fast reflexes or twitchy trigger fingers though, success mostly depends on using the right skill or trap (some have to be triggered manually) at the right time.

Sadly this game seems to be overlooked by most people.

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The Toy Soldiers released on Steam a couple of years back may get a massive update. But to experience that first release in it's updated entirety you have to play it through the sequel (which is currently in Early Access). The first Toy Soldiers is going to be added as bonus content to the sequel.

So if you were planning on playing the first Toy Soldiers and want the 'officially finished' experience you have to play it through the sequel when the sequel goes gold....thus assuming they add content to the first one. They might just tack the first onto the sequel as is like Rayman Legends did with Rayman Origins.

If you're the type who can handle several play throughs of the same game then you might not find it a waste of time to play the updated release when the sequel goes gold. But if there is a significant change to the original's content they should really pull the original from Steam because people are getting ripped off purchasing it for ten dollars when for the same price they can get an improved version + the sequel.

What an appropriate time for GOG's TD games to pop up in the BoftG sale.

Exactly :)

Bloons Tower Defence series - all up in your browser, yo!

Steam tells me that I have 343 hours in Defense Grid, which probably explains why I never finish other games. I don't play it much recently, but it is fantastic fun.

Plants vs. Zombies also filled a lot of down-time for about a year.

I'm agreeing with others who raised these. Based on my joy with these games, I tried a few other tower defense games - iBomber Defense, Sanctum, a couple of others that don't come to mind. They are OK - they are - but they did not grab me the same way, and I didn't play them long.

No, it probably won't. The problem is that one is published by Microsoft. The developers stated when it first went up on Steam that the Early Access version was the original game recoded to take advantage of the PC (and thus, fixing a bunch of bugs in the MS published version) plus the DLC not previously made available on the PC.

The developers also stated that they could do nothing with the MS published version, hence why they have released a new version in Early Access. None of that means you need to buy the Early Access game twice. If you never had the MS published one, then you're getting the full game and bug fixes. If you have the MS published one and want the DLC, then yes, you need to buy the Early Access one, in which case you may as well just wait a few years and get it when it's $2.50. But even then, the games are separate entities as far as Steam is concerned. Saved games from one, may not work with the other.

I agree with the others who recommended Plants vs Zombies. Not only is it the best tower defense game I've ever played, it's actually one of the best games I've ever played *at all* which means a lot since I normally don't even like tower defense games.

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I don't know about most people but If I'm going to bother completing the campaign in the first game I want the complete experience with DLC and bugs patched.

This is what I meant, I was about to install the original version and play but realized the version in Early Access is better.
For the sake of fairness - Once the new one goes gold, Steam should pull the original so that people are not accidentally purchasing an inferior version.

As for games, in general, coming out with better updates and hosting more DLC content (or content in general) at a cheaper price...I've also had my time smugly thumbing my nose at those who couldn't wait and splurged on the original versions.

It just seems to be a status quote in PC gaming that we have to accept

Creeper World 3 - http://knucklecracker.com/creeperworld3/cw3.php

Warcraft 3 (TFT) - if there are still communities up i remember having a blast with some of the custom tower defense maps.

I aggree!

[url=http://en.wikipedia.org/wiki/Defense_Grid:_The_Awakening]Defense Grid: The Awakening[/url] is pretty good. (imo.) ^_^

I haven't tried it myself yet but I have heard a lot of good about Anomaly Warzone Earth. It's a "reverse" tower defense, perhaps it may be of interest to you. -_^