Complete the indicated task to unlock the corresponding guitar at the shop.

Snaketapus: Complete Hard mode.
The Log: Get a five star rank on all songs in Expert mode.
Battle Axe: Complete Expert mode.
Casket: Complete Medium mode.
Eyeball: Get a five star rank on all songs in Hard mode.
Fish: Complete Easy mode.
U.S.A.: Get a five star rank on all songs in Easy mode.
Viking: Get a five star rank on all songs in Medium mode.