As from the sportscolumn.com the top ten sports rivals are.....

10. New York Rangers vs. New York Islanders (NHL)
9. Oklahoma vs. Texas (College)
8. San Francisco Giants vs. Los Angeles Dodgers (MLB)
7. Muhammad Ali vs. Joe Frazier (Boxing)
6. Washington Redskins vs. Dallas Cowboys (NFL)
5. Army ...

If you can boast that people in your town are MURDERED for liking the wrong team come game time, you can boast of a bigger rivalry than Dallas Cowboys vs. Washington Redskins.
This year:
Dallas @ Washington: 4 murders, other assorted drunk-driving deaths
Washington @ Dallas: 3 murders, several ...

Proof?

Huguenots wrote:Thats not an Enzo dude

JHaha, obviously not. But I can't afford an Enzo (and likely never will) so I'll stick with my Cobalt

That's...quite...disturbing

I call the team that hates 'em both: Maryland!
We sell shirts here that say
The Good: Maryland
The Bad: North Carolina
The Ugly: Duke

Living in southern Maryland I can vouch that Fairfax would be an interesting map to play, but also consider Washington DC. That has plenty of monuments and such to make territories out of (although I doubt many people will want to battle over southeast, the gangs would be the army there)