Crystal's Magic Instrument

A guitar that's enchanted to change it's sound based on how the musician wishes it to, so long as a type of guitar could make the sound, also doubles, and triples as two different weapons.   You can use the Weapon Finesse feat to apply your Dexterity modifier instead of your Strength modifier to attack rolls with a Guitar-spear-Scythe sized for you, even though it isn't a light weapon. In addition, the weapon serves as a musical instrument. Particularly fine versions of the weapon can be made to serve as both masterwork weapons and masterwork instruments, providing a +2 circumstance bonus on Perform (String Instruments) checks made with it as a masterwork tool, as well as the normal benefits of a masterwork weapon. Such master-crafted weapons sell for 624 gold pieces.