I got this turd (Counter Strike: Source) for free during the Steam Great Giftpile giveaway thing. I was going to give it away, because I already knew how terrible it was, but I accidentally opened it.
After playing for about an hour, I am reassured of why this game is garbage. No aiming down the sight of your gun? What are they a bunch of untrained monkeys firing from the hip yet still being accurate as long as your cursor is in the right spot.
Everyone argues that this game is good or better than (put in any one of millions of FPS games) because it takes so much skill. But, a game that takes a lot of skill does not make it a good game. Someone could make a Flash game about clicking on a tiny pixel that falls down the screen that gets faster each time or something, and maybe even add multiplayer. Even if I got good at the falling dot game, it's still a crappy game that isn't fun.
Probably the best indie game out on Steam, made by the same group who made Super Meat Boy.
The Binding of Isaac is a heavily Bible-influenced game which gets its name from the Bible story of when Abraham bound his son Isaac to kill him on orders from God. In this case it's your mom who is ordered by God to kill Isaac who escapes by jumping into the basement. The Binding of Isaac will have you fighting the Seven Deadly Sins, the Four Horsemen of the Apocalypse, your own mother, Satan himself, lots of bosses, and tons of enemies in the basement you will wonder what they are doing down there.
The Binding of Isaac is a game of skill, wit and choices set in a retro-styled Legend of Zelda dungeon. Its a twin stick shooter, meaning you move with ASDW and shoot your tears with the directional arrows (preferred) or with the mouse. There are over 100 items that can be picked up to help (or not help sometimes). However this game runs on Flash, so you need a good processor for smooth gameplay.