Starcraft:
Cat and Mice
Kings and knights
Builders and Fighters
Warcraft 3:
Warchasers
Tree Defense
...I like the men in warcraft 3
I don't play Warcraft, but pretty much any Starcraft Defence map's good for me.
I always loved a good Starcraft RPG.
Defense of the Ancients, Defense of the Ancients - Allstars, most Tower Defense games are fun, Peon Olympics, Uther Party, and, of course, WarKart.
Well, most of Starcrafts custom games that are fun are defense games. :/
Battleships!
I've been a Pink Lycanthrope at least a dozen times, and owned every time, so you're not the only one. :)
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I tried playing a little Footmen Frenzy, but the game is just so imbalanced, I couldn't stand it. Then, I tried Enfos, but again, SO imbalanced.
I hate TDs or Mauls because there are always a couple of races/towers that insanely powerful, while the rest are less than mediocre and are about as effective as a one-legged man in an ass-kicking contest.