I recently bought a XBOX 360, and the games I have now are Lost Odyssey, The Orange Box, Call of Duty 4, and Rock Band. So far the most difficult for me would have to be on the Orange Box (Half Life 2 Episode 2) where you have to defend the missile from the stalkers. But the achievement is to not let the stalkers destroy any of the buildings. I'm still trying to complete it. But I wanted to hear from anyone else who has a 360. Oh and your achievements don't have to pertain to the games I mentioned.