That has happened to me in Bioshock. I beat it with default difficulty and then the hard one. I have every achievement except except the one you need to get every audio-diary. Guess what? I missed ONE of the only two diaries that appear in the first level which is the only one you can't go back to. I don't know if I'll ever get that one.
Dead Space. My save data was erased so I would need to beat the game twice to have a chance to get the achievement for completing the game on the hardest difficulty. Maybe one day when I'm really bored.
Wow, you have 1 achievement point more than I do, Kungfuj0. I thought that was pretty funny.
modern warfare 2. i dont even like fps much, dont play them often, but me and a friend rented it and i was able to get 49/50. the only one i couldnt do was get all the stars in special ops. there was 2 i wasnt able get before we returned it.