Fave is hiking, definitely. I love to get out in the mountains, away from all the roads and stupid people around with their giant SUV's (to fight the mall parking lot, of course), and just up in the trees with the wildlife. I love to be able to breathe and get a constant workout just by existing out there.
Second to hiking would most definitely be indoor floor hockey, because I love being able to get that aggression out without actually beating someone up.