Here in Texas the big rivalries have been UT- A&M, UT-OU, and recently Tech-A&M.
The UT-A&M one is so significant because of the amount of venom spewed out by the aggies. As a longhorn, I really don't care all that much, but I am pleased that we beat the crap out of the every year (They f__k sheep, it makes them weak). But thats nothing compared to the hatred and loathing given to us by A&M. Their fight song is dedicated to beating us, they wear overalls andorned with "BEAT tu" (don't ask about the tu thing, its really stupid), they used to light a damn tower of logs that made all other bon fires look like a spark. The scary part is their cult like determination to hate us. People in here may say they have school spirit and all, but CHRIST.
Read this if you don't believe me, its scary.
I deem it the world's biggest and longest case of penis envy in the world.
The only thing I can say about UT-OU game (The Red River Shootout) is that its 5:50, AND OU STILL SUCKS!
..yeah, screw them. If you look at the rankings the past few years, this is usually a top 5 team vs a top 5 team, and where UTs hopes of winning anything significant goes down the toilet.
The A&M - Tech one isn't really all that important, but I just like to tell the story of how, after Tech pummled A&M, the Tech students rushed the field, tore down the goalpost, and threw it into the A&M section while they were still singing the fight song.