Auburn v. Georgia, 2010 at Auburn, the year Cam Newton lead Auburn to a National Title. First time I've ever been to Auburn, my friend's sister was a student at the time. Everyone was incredibly friendly and welcoming, the game was great, very fun atmosphere and first real introduction to the SEC, we were still in the Big 12 at the time. That was a great experience.
2nd favorite memory, Texas Tech v. Texas in Lubbock, circa 1998ish? Both parents are Tech grads. Don't remember the score, or the game really, but I do remember seeing a Tech student steal a t.u. band guy's cowboy hat and running off, and the band guy chasing after him still holding his trumpet, sprinting through the parking lot. No idea if he ever caught him but it was one of the funniest visuals I've ever seen.