Guitars have been heading farther and farther into the extended range for quite a long time now, since Steve Vai popularized the whole 7-string guitar with his Ibanez guitars.  Korn used them in a different way, and tons of bands since have jumped onto the 7, 8, and 9 extended range guitars.  Check out Animals as Leaders...crazy stuff.

For those who want to go absolutely nuts, there's the Chapman Stick, but this guy from Venezuela, Felix Martin, he's basically taken two 7-string guitars and Super-Glued them together.  (Not really, but it works for the image.)

He's really playing two 7-string guitars at once, sort of like Michael Angelo Batio, but all the time.  Check it out.

The bonus?  The music is actually really cool.

And just for fun, here's MAB rockin' the quadruple-guitar thing!