Lost! That is the only one I'm really obsessed with.
I watch a few others occasionally. The Discovery Channel or History channel is usually on at my house, so we like Mythbusters, Dirty Jobs, and the like. I really enjoyed the show Ghost Lab too. I kinda got bored with Monster Quest, cause they never find anything!
Also, I always watch Avalanche games.
Hockey is really the only sport I pay much attention to.
Um... there's a bunch of old shows I used to watch too. Firefly = best cancelled show ever. Watched the first season of The Sarah Connor Chronicles, used to watch House and Bones... Yeah, don't really watch too many shows regularly anymore.