Tioga rubber
I've used the following:
Extreme XC 2.1 - large volume, light for the size, rolls well, corners well on the front (once you have the pressure set right for your weight / style - same as all rubber). Fairly soft compound. Reasonably good grip on the back. A big, light tyre that can cop some curry.
Red Phoenix 1.9 - as big as some maker's 2.0 tyres. Super light, rolls super fast and wears quick. Grip is pretty good early on in its life, even with the low centre knobs. Basically a hardpack and race tyre. I only ever ran these on the back.
Blue Dragon 2.1 - heavy, slow, stiff carcass, not a lot of climbing grip on the back due to the wierd little ridge at the bottom of the knobs. Large volume casing. Wear very fast which is good - you can then throw them as far as physically possible. Only used on the rear.
One of my friends sells GT's and all the 05 and 06 bikes come with the Blue Dragon rear and Yellow Kirin front combo. They are not generally well thought of, a lot of his customers (a lot of them being trailriding types) are replacing them with 2.1 Factory DH's, Extreme XC's or a variety of Maxxis tyres. It seems to me the "trail" tyres, being the Blue Dragon and Yellow Kirin are way heavier than they need to be.