Death by Portal.
Two ways this could work:
1) Someone actually invents a portal gun, and shoots one portal at a wall, and the other one through my head, my brain pops out of the portal on the wall.
2) I'm forced to play Portal over and over again until... due to overexposure, I actually start to hate the game, at which point reality as I know it collapses around me and sucks me into limbo for messing with one of the newer laws of reality. Yes, I love Portal THAT much.