Check out the ESP Mustratangocastinger

[aen]

yeah you can slide/flip the E string nut to the side to use those two extra frets, or just have it standard. i don't really see the point though. i mean, most people tune to drop D in order to be able to play fast power chord riffs with just one finger right? all this does is adding the possibility to play an open D... weird feature, but i think i also have seen it before on a bass.

Yeah, a lot of double basses have these.

Yeah, i was going to mention that,  loads and loads of them have "neck extensions"  with like a big capo thing you clamp and unclamp.  It's becasue LOADS of classical is written around the ke of C, and this device allows you to hit an open C without retuning between masterpieces.