I guess it depends on the sport since I keep up with more than just one.
For those I really pay attention to, I'm a hometown fan.
Football: Seattle Sounders
Favorite Football player: Kasey Keller (unfortunately he is retired but man what a great goalie he was for the U.S.)
American Football: Seattle Seahawks
Favorite American Football Player: I have to admit, I'm forever on that Russel Wilson bandwagon now. I was iffy when we started him, but man that guy is going to take us places if he stays.
Basketball: Boston (That is until Seattle gets our team back, foreverhatingOKC) (But we've got the team practically at this point so I can switch from Boston green back to Sonic green heart)
Favorite Player: Ray Allen. The man is amazing. I don't think we'll see anyone on his level for a while that can make as many 3-point shots as him. I was hurt a bit when he moved to Miami but that's life.