I would think the tuning would most often be (low to high)
B E A D G C F#
So basically a 5 string with an extended high range.
sikth play 7 string i believe
Unearth use 7-strings, you'd probably like them if you like Trivium. A few Joe Satriani songs are on 7-string too I believe (ie: 'Mind Storm')
^Someone should tell that guy he bought a bass instead of a guitar.
I believe Steve Vai's uses a 7-string guitar on the whole WhiteSnake album "Slip of the Tongue" which has some pretty good songs.
Vai's Bad Horsie does too, but you'll need a helluva whammy bar to do that.
Vai uses his standard JEM, no 7 in that song. It's just tuned down a full step from standard with the D dropped to C. highest to lowest, CGCfad