Big 12 Rivalries
University of Kansas and University of Missouri—The Border Showdown (formerly "Border War") includes all athletic events between the two schools. The rivalry ostensibly traces its roots to the 1850s, when skirmishes – widely known as "border wars" – between the two states marked the beginning of the Civil War. See Quantrill's Raiders for more information.
University of Oklahoma and Oklahoma State University—The Bedlam Series encompasses all athletic contests between the two schools.
University of Texas and Texas A&M University—The Lone Star Showdown, modeled after the University of Oklahoma and Oklahoma State University Bedlam series, involves all athletic contests between the two schools.
University of Texas and University of Oklahoma—College football's Red River Shootout. The two teams play annually at the Cotton Bowl in Dallas, with the fans of each side divided by the 50-yard line. The "Golden Hat" trophy is awarded to the winner.
University of Nebraska and University of Kansas— A very old football rivalry (over 100 years old) albeit a lopsided one. Big Red has won 80% of the games played between the two universities Nevertheless, Kansas extracts some measure of blood when the two schools faceoff in basketball.
University of Nebraska and University of Oklahoma— In the old Big Eight conference, the game between the Huskers and Sooners usually decided the conference championship. The Big 12's two-year scheduling intervals have lessened the rivalry between the two schools, but it is still one of the most storied rivalries in the history of college football, highlighted by the 1971 "Game of the Century" between #1 Nebraska and #2 Oklahoma.[2] More recently, the 2000 and 2001 games were both high-profile, "top-five" matchups, with #2 Oklahoma defeating #1 Nebraska at Norman in 2000 and #3 Nebraska returning the favor to #2 Oklahoma at Lincoln in 2001.
University of Kansas and Kansas State University—The Sunflower Showdown includes all athletic events between the two schools. The Governor's Cup is awarded to the victor of the football game. Beginning in 1993-1994 the rivalry lost some of its luster as Kansas State won 11 straight games in football and Kansas won 31 straight games in men's basketball. However, in October 2004, ku beat KSU 31-28 in football and in January 2006, KSU beat ku 59-55 in men's basketball. These games have brought renewed energy and attention to the in-state rivalry.
Baylor University and Texas A&M University—College football's Battle on the Brazos.
University of Colorado and University of Nebraska—This rivaly has grown in standing since the formation of the Big 12. The rivalry was created when then-Colorado head coach Bill McCartney decided Nebraska was Colorado's rival. It has only been in recent years that Nebraska has acknolwledged Colorado is a rival.
http://en.wikipedia.org/wiki/College_rivalry#Big_12_Rivalries