It's Douglas Adams, I mean, really...he was just the best ever.
I do like Dirk Gently better than HHGTTG though, I wish he had gotten the chance to write more than just the two books. And that the BBC series was better than it was. Dirk makes me wish a lot of things actually.
Runners up: Robert Asprin, David Sedaris, Terry Pratchett (duh)