I don't care for the Big XII scheduling. NU and OU should be playing every year around Thanksgiving. It's tradition. K-State has, I admit, risen to rival level with Nebraska since the formation of the North and South divisions. CU (where they are still celebrating the 62-38 win from three years ago) may have designated NU as their chief rival, but the game is only meaningful every few years. CU had a good couple of years, but it looks like the program might fall off for a while.
the biggest rivalries in the Big XII are probably OU-Texas, Texas-Texas A&M, OU-NU, and maybe Mizzou-KU (which is really more of a basketball rivalry).
outside the Big XII Michigan-OSU, Florida-Florida State-Miami, Notre Dame- USC, are big ones that come to mind.
What would sports be without rivalries?