A rivalry has to be felt by both sides. As much as it pains most of us to say it, Iowa fits that bill more than anyone. The dislike runs both ways. That doesn't mean we'd rather beat them than a conference foe, though. Most of us just want a win to shut the other fans up.
As far as a conference rival, I honestly don't see one. KU doesn't see us as a rival in basketball. Hoiberg made some of their fanbase a little anxious, but that's about it. If I had to name one, I think they enjoy beating KSU more than anyone because they don't want to lose that in-state battleground. With Wichita State asserting themselves, KU doesn't want to be perceived as being 2nd or even third best.
In terms of football, I don't know any team that considers us as a rival yet. If we can flip the script on KSU, I think they would be our most likely option, but losing 10 in a row does not make a good rivalry.