Well, I’m from Boston, so:
MLB: Red Sox
NHL: Bruins
NFL: Pats
NBA: Celts
NCAA Football/Hoops: BC
NCAA Hockey: RPI
NFL: My beloved Dallas Cowboys … might be in for a bit of dry spell for a coupla years. I’ve been with them for 30 years or so. I went through the brutal 1-15 season with them, although at least that year we beat the hated Redskins (and swept them this year)!
MLB: Atlanta Braves, since I lived in Georgia for a long time and then moved to Florida before we had a team.
NBA: Orlando Magic. I’ve been here since the beginning … it’s been another rough year, but Tracy MacGrady is making me a believer!
NHL: Buffalo Sabres, I guess, for no particular reason.
NCAA Football: University of Georgia (Alma Mater) and Florida State (Gator’s other worst nemesis)
XFL: I’m going to have to attend at least one Orlando Rage game this season!
College anything: UCLA BRUINS, UCLA BRUINS, UCLA BRUINS, UCLA BRUINS, UCLA BRUINS.
And UCLA BRUINS.
As to professional sports, I play in multiple fantasy leagues (~10 baseball leagues, 3 hockey, 1 basketball and 1 football). Players on my fantasy leagues have my first loyalty.
That said:
NHL: LA Kings. Even though I used to work for the guy who owned the Kings, and he shafted his employees. Then he went to jail.
MLB: California Angels. Second favorite is LA Dodgers.
NBA: LA Lakers. I root quietly for the LA Clippers when I want to display compassion (You know, the old “I’m a sensitive guy with feelings” schtick)
NFL: Don’t get me started about LA not having a professional football team!! :mad: Rams and Raiders by default.
At first Goose, I liked you…
And then you became my enemy…
As a current MSU student, I am and always will be a die-hard Spartan fan. I can’t wait to see us repeat as national champions, 3-pointers at the buzzer aside.
Actually, I don’t care much for basketball, but I root for the Pistons because Mateen is on them and Toronto cause Mo’ P plays for them.
In college sports, my second favorite is usually Notre Dame. My third favorite is whoever is playing Michigan. 
Goose, at least tell me you or a close family member goes or went to U-M. The thing I hate is people who blindly root for them despite having no affiliation to them whatsoever.
MLB 1) The Dodgers 2) The Angels. I’m a National League guy, but the Halos are local to, and have a great stadium.
NFL The Bengals. Pity me.
College Football The Ohio State Buckeyes!!!
I don’t watch any other sports.
Another Bostonian, now far from home.
MLB: Red Sox, until the strike. Now, I don’t really care
NBA: Celtics. Darn shame what they’ve turned into.
NHL: Bruins
NFL: Never really cared
In my new home,
Baseball: Yokohama Baystars. I used to like the Chuunichi Dragons (cool name) until I saw what a complete asshole coach Hoshino was. He beat an umpire badly enough to break the guy’s ribs, and only got a 5-day suspension. Nothing he’s done since indicates that this “punishment” taught him anything.
Soccer: Jubilo Iwata. No, I’m not just cheering the front-runners. I lived next to Iwata for 3 years.
–sublight.
I’m a homer, so most of my teams are predictable.
NHL: Capitals
NFL: Redskins
MLS: DC United
MLB: Don’t care for baseball, but prefer the O’s.
NBA: Don’t like basketball, but prefer the Wizards.
College football: Virginia Tech. We’re losing Vick, but at least we’re keeping Beamer.
Other soccer: Real Madrid (Spain) because I had a friend who lived in Madrid with rabid Real fans. Juventus (Italy) because I played with a kid who later had a tryout with the club. I don’t really have an English club I support because I don’t have any connections through friends or family to any area. I just root for Man Utd to lose because I’m an American and root for the underdog. For national teams I root for USA and Italy. I root for Italy because of my ancestry and because I started watching soccer back when the US team couldn’t qualify for anything.
MLB: Cleveland Indians (primarily), Pittsburgh Pirates.
NFL: Pittsburgh Steelers.
NHL: Pittsburgh Penguins.
NBA: Don’t give a rats ass. If I had to pick, I’d pick the Cavs.
College Football: Cornell. Hey, I just don’t care about college football that isn’t being played by my school. Doesn’t interest me in the least.
College Basketball: Same.
College Hockey: Cornell…but I do care about college hockey in general. I’m such a hockey nut, so it’s great that Cornell actually has a good team almost every year. Makes things fun for me! (Go Red, beat Vermont and Dartmouth this weekend!)
Thems my picks.
Jman
Hmmm. I may have reconsider my earlier idea of remaining civil then.
Nah, we’re kind of indifferent I guess. The man was a great player here and people still love him (we’d love him more if would learn to keep his mouth shut once in a while in matters of religion and politics). When he left the Eagles as a free agent, he really took a chance on little ol’ Green Bay, and that opened the door for other good players to look at the Packers as more than just a small market mediocrity. Without Reggie, there would probably not have been the influx of talent that got signed in GB during the 90s, so he gets a lot of credit for the Super Bowl season. But he battled a lot of injuries his last couple years and everyone knew he was going to retire. I think Packer fans are pretty forgiving when it comes to their fan favorites. Hell, even Mike Holmgren got a standing ovation when he returned to Lambeau for the first time as the coach of a different team, and people were more than a little bitter when he left.
Of course, if Reggie had signed with a team in the NFC Central then he wouldn’t be able to show his face in Green Bay ever again. We’re not that forgiving.
Good idea, Fletch. Here are the teams that I hate (‘sports’ hate, of course, which is qualitatively different from the real thing):
Most despised, NBA: Los Angeles Lakers. Shaquille O’Neal gets away with more illegal defense than any three other NBA centers put together. Plus I’m a Blazers fan.
Most despised, MLB: New York Yankees. Being an Orioles fan and a champion of more salary equity in sports (yeah yeah, the irony) makes this one easy.
Most despised, NFL: Dallas Cowboys, natch.
Most despised, college football: Notre Dame for their TV deal, UNC for their being UNC, and the bowl selection process just 'cause it’s horribly unfair.
Most despised, college basketball: I went to Duke, so the answer to this one should be self-evident. University of North Carolina Tarheels.
MLB: New York Yankees
I’ve been following the Yanks daily since I was a wee tyke in 1978. I was even there checking scores and highlights every night in the low late 80’s-early 90’s period. These last few years have been very good to me.
NBA: Boston Celtics
I don’t follow them as closely anymore now that they’ve sucked for so long.
Most despised: Dallas Cowboys, Dallas Stars, Texas Rangers
Nothing like local hype and homerism to lower my esteem. How I love to see these teams lose. 
Since I went to UNC, I guess that makes us natural enemies, eh? Go Heels! I definitely remember that game from your OP though. One of the greatest rivalries ever, we can probably agree on that at least.
Favorites:
NBA: Charlotte Hornets, just cause they were the home team, though I don’t pay as much attention to the NBA as I used to.
MLB: Don’t care much for baseball, but I’ve had two roommates in the past who were big baseball fans, and they pulled for the Chicago Cubs and the Cleveland Indians. I just decided to pull for them to because it seemed like the easiest thing to do.
NFL: Really don’t like football. I live in Nashville now, though, so I guess I’ll pull for the Titans. Whatever. I’m a basketball fan in a football town.
Least Favorites:
NBA: Nobody right now. I hated the “Bad Boy” Pistons from way back, and then I just got really really sick of the Chicago Bulls winning all the time… not a problem anymore, is it?
MLB: Chicago White Socks, for much the same reason as my listed favorite MLB teams
NFL: 49ers, Redskins, Packers, and every other team people get way too worked up over.
Sox. It’s spelled Sox. I know this.
drewbert: Absolutely the best rivalry in college sports, at any rate. 
Maybe matched by Celtic/Rangers worldwide.
Glad to see you guys finally recalled Carmichael and put the students near the floor! That place was rocking during the Wake game… What years did you go to UNC?
Like Gadarane, I also live in Oregon, so that has influenced a couple of my choices:
Favorites:
NBA: Portland Trail Blazers. True, Brian Grant going to the Miami Heat was a great loss, but it didn’t hurt me as much as what happened in the first eight minutes of the fourth quarter of Game 7 against the Lakers in last year’s Western Conference Finals. That was pain…
MLB: I watch more Seattle Mariners games than any other team, simply because Portland gets a lot of their broadcasts.
NFL: Tampa Bay Buccaneers. Before moving to Portland at the age of 10, I lived in the central Florida area. My relatives are still there, so I visit the region frequently. The Buccaneers were the first pro team I ever took an interest in.
College: For football, I pay attention to the Florida Gators, the Oregon Ducks, and the Oregon State Beavers. I loved every minute of the hurt the Beavers put on Notre Dame in the Fiesta Bowl. For basketball, I don’t really follow it at the collegiate level, although I do watch the NCAA championship game.
NHL: I don’t really pay attention to this league.
MLS: You must be kidding.
College: The University of California Golden Bears. I must’ve been very bad in a previous life. But I’m mousing on a script-Cal mousepad even as we speak.
Most-despised, college: USC. Arrogant, and their band is obnoxious.
MLB: SF Giants. I’m proud to say I saw Mays, McCovey & Marichal play.
Most-despised, MLB: Yankees. When I was a kid, rooting for them was like rooting for U.S. Steel, as the saying goes. Add a dose of Steinbrenner, too much money, and New Yorkers in general, and you’ve got a lethal combination.
NFL: I wish the 9’ers and Raiders well, but basically don’t care. Like to watch any good game.
NBA, NHL…yawn.
I didn’t know they did that! I hadn’t been keeping up with the student vs. alumni seating problem since I left Chapel Hill. Great news! I went to school there from '91 to '95, then worked there until last September.
NFL: Buccaneers and Dolphins.
XFL: Orlando Rage and Chicago Enforcers (Chicago is currently practicing on my school’s back-up football field. It’s pretty sad.)
NBA: I’d say the Magic about 6 to 8 years ago, but now it’s not really any team.
College:
Basketball: Duke is cool, but I like Michigan State this year.
Football: Florida Gators.
No NHL or MLB team, really.
NHL: Detroit Red Wings. I grew up in the Detroit area, they’re my home team.
NFL: Jacksonville Jaguars. I live in Florida now, and they’re my adopted home team (I didn’t really follow football until after I moved down here).
Those are really the only team sports I follow, but I’m an auto racing fanatic:
F1: I’m torn here. I love Ferrari, but I hate Schumacher. Hakkinen is my favorite driver.
CART: Forsythe Racing is my favorite team because I’m from Canada originally, but Castroneves is my favorite driver.
NASCAR: Rusty Wallace. He just seems like he’d be a cool guy to hang out with. The new Dodge team will be interesting, too.
Sports cars: For prototype cars, it’s Cadillac. The cars just look real classy with the Cadillac grill and their gold and black paint, and it’s American. In GT2, Team Oreca Viper. American muscle running circles around Porsche (my most hated team)! Woo!!
MLB: Baltimore Orioles. My home team, who I love as much as any man can love a sports team. I’m originally from Philadelphia, and in the NL I root for the Phillies, as long as they’re not playing the Orioles. What I’d really love to see is a rematch of the 1983 World Series.
NFL: New Orleans Saints. It used to be that I rooted for any team who played against the 49ers, but I got to liking the Saints more and more over time.
NHL: Philadelphia Flyers. As a kid I attended many Flyers games, and am proud to say that everything they say about fans in Philly it true. I watch the Capitals on TV, but the Flyers will always be first in my heart on the ice.
NBA: Philadelphia 76ers: See above. The only difference is I never watch the Wizards. They’re embarrasing.
Teams I hate: New York Yankees, San Francisco 49ers, Atlanta Falcons.