David Blaine has a really cool trick involving about a gallon of water, some kerosene, and fire. When it works as intended, he chugs the water first, then swallows the kerosene, which he then spits out to light his logo on fire. Once it's lit, he puts it out by spitting water onto it. Absolutely marvelous effect that nearly went very, very wrong during a performance for Microsoft interns.
As you might imagine, blowing out enough water to douse flames requires a fair bit of effort (read here about the lengths Blaine went to in order to make it work), and on this particular day, that effort was too much for him. As he explained to a packed ballroom at Genii Convention in Orlando, he briefly lost consciousness as he was dousing the flames, and started to fall over. Luckily, he woke up just in time to catch himself and finish extinguishing the fire. Another second or two and he'd "have a big 'DB' branded on his face," he said jokingly.