Newport Stadium, hands down!!! Nah, really I can't believe that noone mentioned CovCath. I know that Saturday's aren't the same as Friday's in terms of atmosphere, but if you have ever watched a CovCath-Highlands game there you would agree. The student body is what gives the place it's atmosphere.
Also, as a one time thing, the best atmosphere I've ever been to was Highlands-Elder at Paul Brown Stadium. It was cool to see all of those fans to watch a match-up of nationally ranked teams.
I must stop now b/c I've filled my Highlands quota for one post. As a Bred's fan, I can't bring myself to say the name again, ha ha.