When Splinter Cell: Chaos Theory came out a few years ago, I got stuck very near the end of the game in the last 2 minutes of the second from last level. It was in the room with the bombs that Shetland set up, right after you walk out the door and him and Sam have a little talk, then it's straight on to the finale.
I had to give up for a few weeks. I had 3 guards on me, I was backed into a corner, and I'd saved at exactly the wrong moment, so every time I booted up I had about 3 seconds to move out of position, reload my gun and hide. And the health bar had been reduced to the size of a gnat's cock which meant I couldn't get shot.
Bloody near-impossible.