I'm a big fan of the Durkee's Hot Sauce. It's not really all that hot, but it adds sooooo much flavor.
The hottest i've ever had was called "Pure Cap". It was concentrated pure capsicin (sp), which is the chemical that makes hot peppers hot. I had ONE DROP on a soda cracker (from an eyedropper) and I was in tears for half an hour, and I LOVE hot food.
I gave my dad a bottle as a stocking stuffer that year. <evil grin>