Ow. I like things a lot hotter than most, but I think I hit my limit around where people start having competitions about it.
I make quite a firehouse chili, though, and some pretty serious curry, if people are in the mood.
I think going overboard can often just ruin the flavor, so I like to use lots of mild-to-moderate chilies and then just punch it up with a bit of the very-hot hots.
I like to use poblano and chipotle, then add some stuff I get at the Indian market.
Last years' gardening was hard, mostly all we got was a *ton* of jalapenos, with which I gave myself minor chemical burns on one occasion.
(Though there's a place in town I know that makes quite a habanero sauce. Whoo. Run by a very nice lady, too. )