Arranged in the order I care about them:
MLB: Red Sox
NFL: Vikings
NCAA FB: The Ohio State Buckeyes
NHL: Bruins
NBA: Celtics
NCAA BB: Duke Blue Devils
Premier League: Manchester United
MLS: Revs (But my favorite soccer team in general is the Dutch Men's National Team)
AFL: Soul
WNBA: Suns (Only because they play at one of my favorite casinos)
Why do you like the Vikings?
As a kid, I worshiped Brett Favre. I followed him around from Green Bay to the Jets to Minnesota. After he retired, it was easier to stick with the Vikings rather than replace all the trinkets around the house and pick a new team. Although, to be fair, I do root for the Patriots once the Vikings are out of contention.