For me it's Smashing Pumpkins. Their sound spans so many genres and effortlessly transitions from hard/heavy on one number, to soft/celestial on the next, sometimes within the same song. People knock Billy's voice but I think it's quite emotive and suits the songs perfectly. Plus Jimmy Chamberlin is one of the greatest ever behind the kit. I'm not necessarily a big fan of the newer stuff, but they were a force of nature in the 90's.
