I don't like stuff that's too hot, so I don't have voluntary experiences to report. I did buy once at a local farmer's market what's touted as the hottest pepper in the world, called naka jolokia, from India. I did not use it to cook, though, so i cannot attest. Apparently, in the region where it's grown in india they do pepper eating competitions. People don't die, but regularly pass out.
My worst experience eating something hot was in a "temple cooking" restaurant in Korea. Tricked by a glowing review in the NYC (presumably by an anorexic journalist), I tried. The food was awful overall, but one of the worst moments was when from the little dishes of steamed weeds I was served, at some point I inserted into my mouth what turned out to be the hottest thing I ever put in. It wasn't red, and I don't know what it was (probably more like a wasabi type of veggie), but I nearly passed out. I wasn't the only one. A few minutes later, from a nearby table with local youths (who had earlier watched the foreigner's mishap with some amusement), I heard a woman scream and the male companions shout for water...
cacio