Tower Defense

Okay, so this one has already been all over Digg and everywhere else, but somehow I missed it until recently - I may have passed it over because the graphics looked kind of cheesy and the gameplay didn't seem very exciting. But...well, I actually kind of like this game. It's very simple, you just place these towers and they stay still shooting at the line of baddies that are trying to get you. You get gold, which you obviously use to build more towers. It gets hard after a long stretch of easy - perfect lunch break game, you'll probably finish your second attempt at the game right about the time you need to go punch back in or go to class.

By the way, there is also a sequel to the pictured game, called Flash Circle TD, which looks pretty cool. Have fun!