I live in Northwestern Ohio, so I have no local major league teams to be a fan of; but my favorites in football, baseball, basketball, and hockey are the Cincinnati Bengals, the Cincinnati Reds, the Chicago Bulls, and the Columbus Blue Jackets.
Of cities that have two or more teams in those sports, my allegiance goes as follows....
NFL:
New York = Jets (I like the AFC better than the NFC.)
San Francisco Bay Area = Raiders (The 49ers beat the Bengals twice in the Superbowl

.)
Washington D.C./Baltimore Area = Baltimore (Again, I like the AFC.)
MLB:
New York = Mets (The Yankees =
PURE EVIL!)
Chicago = Cubs (I love an underdog.)
Los Angeles = Dodgers (Who can't like the Dodgers?)
San Francisco Bay Area = Giants (I used to be a Barry Bonds fan.)
Washington D.C./Baltimore Area = Orioles (Again, I like an underdog.)
NBA:
New York = Knicks (Hell, for the longest time, I didn't even know the Nets existed.)
Los Angeles = Clippers (Again, I love an underdog.)
NHL:
New York = Islanders (Hell, I'm just picking at random. I hardly follow hockey at all.)
Los Angeles = Ducks (Again, I'm just picking at random.)