I bought myself an xbox 360 controller last week. I pretty much only bought it for one game, but I love this thing so much I started to look specifically for games I could play while laying motionless on the couch. I'm sure this is old news for most of you, but these things are amazing. Especially if you have your pc hooked up to a TV with Steam in big picture mode.
Highly recommended. Only downside is I don't have many games that support it. I finished A Tale of two Sons and replayed Limbo and now I'm out of games.