NCAAF: Huskers, but I like watching a good game with other teams if nothing else is on (could really care less what the final score would be for those games)
NCAAB: Gonzaga, pretty much in March. Only the Zags because it seems that's all I get
NFL: Seahawks. Growing up in the Pacific Northwest, they've come second in my heart (after the Huskers of course)
NBA: I don't think I've ever watched a full NBA game :dunno
MLB: I'm embarassed to admit this, but LA. Once football season starts though, I could care less about baseball.