Pregnancy tests. That's probably pretty self-explanatory ;). As far as "thrill" kind of butterflies, that would have to be one of my favorite pastimes as a teenager, which of course I'd now look back on as completely stupid and foolhardy -- antelope chasing. I had a pride-cut Mustang who was rounded up from the wild horse preserve when he was seven, and never really completely tamed down. I'd take him out in the badlands and we'd go charging after the antelope (pronghorn) at breakneck speeds -- it means complete trust that your horse won't stumble or shy (or randomly veer off just because he feels like it), even while he has antelope darting under his belly, right under his nose, and directly behind his hooves, sometimes running right into his flying tail. The badlands where I grew up had very broken terrain, holes from snakes and prairie dogs, ravines and gullies everywhere, and all sorts of wonderful opportunities to get oneself killed.
Seems like my first few times whitewater rafting had the same sort of effect, but my dad owned an 8-person raft so we used to do runs on the Snake and Shoshone as often as twice a weekend during the warm months. It's still fun, but the thrill started to wear off.