Depends on the application.
Bloody Mary - horseradish and tons of tabasco
Food - Jalapeno's diced and mixed in. Close friends, we toss in a couple habaneros.
Our local Thai place has a heat scale 0-10. It took us a couple years but we're now ordering 10 for curry and 8 for noodles. Damn hot but so satisfying.
I am from European decent, but was raised in SoCal. Love me some spicy food.