PC: Super Meat Boy. One of the best and most challenging platformers I have ever played. I am not good at games in this genre, but it was very cheap during the Steam Christmas sale. I've reached hell and completed half of the levels there, done a few retro stages and completed a few Dark World levels.
When the challenge is driving me crazy, I go to the PS3 and play Demon's Souls. Killed 4 bosses and killed some mini bosses. I'm getting a better grip of the game and dying a little less than I did in the beginning.