This pertains to both football and basketball. I had a really memorable, bad experience with SDSU football fans when I was younger (probably 14). They insulted my family and I until my brother and I stood up to fight them. That shut them up. The score helped a lot too.
As far as classiest fans goes, I've had some really good experiences too. Boise State fans seems pretty tame. I met some really nice Oregon State fans as well.