Rivalry infers two players who actually WANT to fight one another, that the balance tips back and forth occasionally and that the winner takes joy in beating his opponent. In that light my biggest rival for a long time was SHawk back in the days we were both at or near the top of the overall rankings. He was always vocal after his wins. Not so much after his losses. Second on the list probably goes to that Aussie Yak T pilot (forgot his name) of several years ago. I might have to add NIKL5 to this list simply for his obvious glee on 200 when winning.
Good fights/pilots over the years but not necessarily rivalries go to Slapshot, NB, Ack Ack, Cobia and other's I've forgotten.
Finally, Fugi, give it up. After all these years the few times I've ever run into you in the arena you've been embedded in the midst of a red horde and the few times you've beat me you were like the fifth guy in. Play how you want but stop preaching. We all know who the top fighters are.