I see this question two different ways. Ichiban, a match that was scheduled in the cannon but didn't take place because a team won. Niban (yes I have), a match that I would like to see take place.
Ichiban - hum, I'm actually at a loss trying to think of one here. I guess any of the Seigaku singles 1 games that never took place.
Niban (yes, I have) - I'd love to see the Platinum Pair (Niou and Yagyuu) take on Koharu and Yuu-kun. I think that would be a match made of awesome.
bonus points to anyone who can get the niban joke in here, btw. Ro and I love that part.