Worst one I-as-player ever had?
My previous PC had died and I needed to bring something new in. Well, in this case something new meant something old: as I had some spare PCs booting around the game world the DM found a way to bring one in, the story being he'd been adventuring on his own and ended up as a prisoner in the complex the party was exploring.
The DM places me in the dungeon and he and I both wait for the party to find me (my character was known to half the party but they had no reason to think I was there). And we wait, and we wait, and we wait. For five sessions, as the party explores every possible bit of the complex except the part I'm in (and as I also don't know where my PC is, I can safely play a party NPC in the meantime, which I did).
Then at last they find me, strapped to a torture table that hyper-magnifies the effect of any touch or contact. One of the the other characters who recognizes me rushes over to the table, "Hey, it's us - what are you doing here?!", and slaps me gently to wake me up.
The table magnifies the gentle slap into a thunderous blow.
Broken neck.
Dead.
Sigh.