Funny you imply an addiction. The pepper sensation I'm currently in love with doesn't even come from a "hot" pepper, it comes from Szechuan peppercorns, which you usually won't find in typical Americanized Chinese restaurants. It actually sort of numbs your lips, or they kinda feel like they're buzzing. It's weird.
As far as hot goes, if you're not overly familar with the really nasty peppers,
here's a list. However, you can't take that list to the bank. My personal comfort level these days usually tops at 100K Scoville, but used judiciously. After that it's mostly pain, no flavor. But I got ambushed at an Ethiopian place in DC with a batch of piri piri peppers (normally in the 50-100K range, but can go up to almost 200K) used in a sauce that were clearly well north of my tolerance. Hate it when I get surprised like that.