2. Florida Gators/FSU Seminoles (football). The second greatest rivalry in all of sports? Are you kidding me? It's a good one, to be sure. But #2 on the list? Uh....no.
It may not be # 2 overall, but it is pretty good. Always played as the final game of Florida's regular season--if you lose that one, many times it detracted from what you accomplished over the previous 10-11 games.
A close second for Florida in its football rivalries (some would argue it is #1) would be Georgia. I have to give the nod to UF vs. FSU because of their proximity and overall longevity of solid football excellence.