fr33kSh0w2012: Say you were in prison on death row and they let you have time to play one last video game before they ended your life.
Dunno, not a very original answer but if I didn't have anything better to do with my time and I had to choose one, maybe Planescape Torment, in order to remind me how tormenting immortality can be? And also because it's one of the longer games I've played, granting me more time. ;)
Or maybe one of the mods that I created with a friend or family member, to remind me of the good times.
Or maybe just something pretty trivial but addicting, to keep my mind off the impending doom? Like a casual game or lighter RPG or action game / shooter?
Or preferably something really educational about prison breaks and weapon handling. Or Psychonauts' Meat Circus, to build up enough rage to overpower the wardens, or enough despair to embrace death with a relieved smile. :P