Expert: LeenyDMB41 - 2/12/2004

Question
what brand of guitar does dave use?

Answer
From Gearbox Magazine:

Dave Matthews plays a Gibson Chet Atkins model guitar. "I'm spoiled," Matthews confesses, "I just describe what I want to hear or what I don't want to hear and leave the rest to Monk." For his part, Monk (Matthews' guitar tech) says, "Dave's playing style demands clarity. Each piece in his rig was chosen with that in mind. I believe that this system gives us the truest representation of the Chet Atkins' acoustic qualities. Almost everything is run flat to achieve this. The White EQ processor 5024 is our master EQ. We pink-noise the system [using a spectrum analyzer to examine and equalize the frequency response of a room] to replicate stage sound. The results have been excellent. Up to this date, Dave has never really used effects, but I believe by the end of the year he will be using an Eventide 3000 GTR Harmonizer."
--Andy Markham

Sorry that wasn't my own answer, but i think that will help you out a whole lot more than i could considering im not the biggest guitar expert.  I DO know that he has also used Martin and Taylor guitars in the past, and they are pretty darn expensive.  I hope i could help, and im sorry it took me a while to answer this, but ive sort of been out of commission for the past few days! Hope this helps!