Penn State, Virginia Tech, Miami, and West Virginia would be on my Mt. Rushmore of hate. These are the only opponents that have really moved the needle of hate against us in my lifetime. We dislike BC, but it's not at the same level. We've played Pitt forever, but we're almost never both good at the same time. We don't like Rutgers or UConn, but that's mainly because they're scrubby little programs with delusional fanbases that had asswipe coaches(Edsall and Schiano). But they've never been good enough to really care about, and now that they're not in our league I couldn't care less.
Penn State was a yearly matchup right up until we started beating them and the series ended in 1990. We only recently played them again. Throw in all their issues...they're just kind of disgusting all around.
Virginia Tech was a very good rivalry from the mid 90's to the early 2000's. We played a lot of big games against them, battled for the BE title many times, had some great games and some embarrassing blowouts(both ways), their coach whined and made excuses every time we beat them, and their fans were just a different breed of weirdness. I felt like they were starting to be solidified as "THE rivalry" game for us, but this suddenly ended when they left the Big East in 2003. I was really hoping we'd get in the same division as them in the ACC so we could rekindle the rivalry.
Miami - who doesn't hate Miami? They were the program we most wanted to beat in the 90's when we were good and felt like we were on the verge of being a major powerhouse, but we usually came up short against them. Throw in that they're also disgusting like Penn State, and they're very easy to hate.
West Virginia was a longtime rival that lasted right up until the demise of the Big East. There were some GREAT games in this series, and some heated moments(bench clearing brawl in '92, their idiot AD Oliver Luck popping off about us and saying he'd rather have Navy in the Big East over us after it came out we were leaving, etc.).