Funny story. At Christmas, my friends gave me a bottle of hot sauce that they had never tried, but knew to be pretty hot (it is made with Habanero, Naga/Jolokia, and Capsaicin crystals). I didn't try it before bringing out to use in a restaurant for breakfast. Luckily I decided to try a little first before pouring it on my food. I dipped one tine of my fork in it and tasted it. I couldn't feel my tongue for five minutes. I am not exaggerating.
Well, the owners of the restaurant (this was a Korean family place) saw me tasting the hot sauce and they all wanted to get in on the fun. I warned them to try just a small amount before pouring it all over their food and not being able to eat it. One of the waiters took a toothpick and only put about half a toothpick full in his mouth. He turned bright red and literally couldn't breathe. I was worried that he might have a heart attack or something. It took him about ten minutes to regain his normal colour.
I don't think I am welcome there any more...