I have 2 times where i wanted to literally rip my hair out.
#1 In CoD, i forget the name of the level, But your in the television station, that room with al the cubicals. Ugh, i had to try that about 20 times to get it right. and then i couldnt beat it again.
#2 In mass effect, my first play through. I got to one of the first "main quest plaents" after saving liara and doing every side quest to that point. I cant remember what the name of the planet was, but it began with an F, and it had that big plant creature thing under the citizens. Anyway, after i do the whole level and get to the very end, im in the elevator that has a load screen, and i save as soon as i get done with the load. I only had one save at the time (stupid me) Anyway, i didnt want to kill any civilans, so when killed one by accident, i tried to load my other game, only to find that when it loaded, i was stuckin the elevator because the door was glitched. I looked it up online and found i had to start the whole game over. It was so messed up.