Unwinnable by Mistake/Video Games/Prince of Persia

The Two Thrones

Prince of Persia: the Two Thrones has a glitch that makes a critical jump unfinishable. The only way to progress if you strike that bug is to download a savegame from someone who didn't.

Prince of Persia: Warrior Within is riddled with Game Breaking Bugs that can land you in Unwinnable situations:

The "Sand Wraith bug," which occurs early in the game if you save in the wrong place, gets you turned into the sand wraith before you're supposed to. The subsequent Unwinnable situation happens near the end of the game, right before the final boss. You end up having to start the game over after coming all that way.
A different glitch with the same ultimate result: You can glitch right before the final boss if you go back to the previous room to save before going through the portal. When you return, the portal will no longer react -- and you can't go further back than the save point.
Other unwinnable situations arise from oversights rather than glitches. In some rooms, it is possible to move platforms to locations other than their intended ones and still exit the room if you do it all fast enough. When you return to those rooms as the Sand Wraith, the platforms will be too low or too far apart to make it across.
Late in the game, it's possible to return to various sections to collect upgrades you missed earlier; but, due to a glitch, one of them is a dead end with not one, but two, save points in it, making it easy to save yourself into an unwinnable state.

In Prince of Persia: Sands of Time, there's one room near the end where Farah waits by a switch. She will not pull it until you complete a set of puzzles. Once everything is ready, Farah should pull the lever automatically... but sometimes she doesn't. She will stand there silently while you jump around in anger and grope for the 'reset' button.
There are two areas in the game where you can fall off beams, survive the fall, but fall too far to get back to where you were, making the game unwinnable.
Late into the game,there is a puzzle section that is immediately preceded by combat. The puzzle requires you to make a few jumps that deal a small amount of fall damage. Unfortunately, there is no way to heal after the combat, so if your health is low, you cannot continue.