The blue Fender Mustang played by Kurt Cobain in Nirvana's "Smells Like Teen Spirit" video is headed to the auction block. The guitar, which has been seen by more than 1.4 billion YouTube viewers, will be offered next month, says Martin Nolan, executive director of Julien's Auctions. "This is one of the most iconic guitars ever to come to the auction block; one of Kurt Cobain's favorite guitars of all time," Nolan says. "The guitar comes with its original case and, also, the guitar strap." Fans of the late grunge icon should probably start saving their money immediately. Julien's officials are expecting the guitar to fetch between $600,000 and $800,000 when it's offered from May 20th through May 22nd -- and "that's a conservative estimate," Nolan says.