OT: Arch Enemies

Who do you guys think were the best arch enemies in sports or even life?  Not necessarily a rivalry, but two people that just hated each other. Could be on the same team even.

Also, I need a new arch enemy because apparently RGard left unbeknownst to me.  He didn't even give a parting shot.  Very disappointed that he went down that easy, but not a shock that I am the victor once again.  The Koala is superior to the Gibbon as I am sure you all knew.  I hope he will give his mother my regards as I must move on entirely. 

DISCUSS.