horror movies, I'd say... I love sitcoms, stand-up, gag strips, but it's rare that I've found a film that makes me laugh throughout; whereas horror films can make me scared throughout! Also, I like that peculiar way in which horror films play it totally safe, yet transgressive!
Truth serum... I'm already lucky enough to be loved by a good person and I'd feel skeezy using one. A truth serum however would keep me occupied for years, like some mad justice-obsessed superhero, exposing the secrets buried in the hearts of men (I suspect that few would thank me in my task!)