The longest-running rivalry in modern metal pits Mushroomhead against Slipknot, a conflict that continues its inexorable march toward some sort of Wrestlemania resolution. The feud started back in 1999, when Mushroomhead accused Slipknot of stealing its creepy-mask shtick, and it's only become more heated in recent years. Mushroomhead ridiculed its nemesis during a Halloween 2006 performance, then posted a parody of Slipknot's album artwork on April Fool's Day 2007. Mushroomhead looks much scarier than its archenemy: Its members' masks resemble actual rotting flesh rather than rubber disguises. The group's gory video "12 Hundred" contains more disturbing imagery than all the Saw movies combined. Judging on musical merit, it's a draw, with Slipknot weighing in heavier and Mushroomhead connecting with stronger hooks. Mushroomhead hasn't strayed far from the late-'90s nü-metal blueprint, with eerie keyboards, turntables, chugging riffs, and choppy shouts, but Waylon Reavis (singer since 2004) has attracted mainstream radio attention with his rock-idol pipes.