Guitar Hero: Metallica has popped up on GameStop, along with an interesting bonus for pre-ordering the game. According to the site, the game will include a bonus drum pedal, along with a splitter, which will allow would-be rockers to drum with dual pedals if you order early. You know, just like Lars Ulrich.
The listing is for the Xbox 360 version of the game, but it's a safe bet to expect this for Wii. It's a multiplatform game after all and if one version is going to offer dual pedals, we doubt it would be excluded from the other versions and a bonus exclusive to the Xbox.
Update: Added further clarification that this is a pre-order bonus.