A must have if you like rougelikes. Lighthearted, funny and challenging at the same time. Have been pretty much constantly playing since purchased. For those who are unfamiliar with rougelikes it has some optional difficulty settings, and allows one to turn off permadeath (though you'll want to keep it on for a real challenge). This would definately be the entryway game for people who have never played a rougelike before. Oh, it's also only $5, so get it you murdurous sneak.

Great adventuring/building game.

An amazing game which I keep coming back to. Very high replayability thanks to it's various weapons, and perk systems. The game is immensely challenging and feels very rewarding, and has many different maps to play on. Tons of "zombie" (really zed) killing, and it's as mindless or thoughtful as you want it to be. Be ready to lose, often, and laugh at how horribad things went, but when you win break out the lube and party. The very best part? You can bring 5 of your friends along for the ride. Just to hear them shout out some very bad british voice acting and then get instagibbed by a fleshpound, hilarious. It gets even better when you win with a well co-ordinated team.

This game is a must get if you're a fan of co-op survival horror games, seriously.