What does this involve? Beating the game without dying?
The best achievement I have ever received from a video game, was taking the gnome to the moon in Half Life 2: Episode 2.
You found a garden gnome at the beginning of the game and would have to pick him up and carry him throughout the entire game, to put him inside of a satallite at the end before you launch it. Quite a complicating burden in a first person shooter where you are trying to fight off aliens.