(– by hustler #5243 –)
I have a set of Falken Wild Peaks (called a Rocky Mountain ATs if you get it from Discount Tire) on my Jeep. They're great everywhere – quiet on the street, lots of wet road traction, and even worked fine in the mud. Last weekend I ran the Rock and some other trails and got stuck in a sudden and fairly substantial rain storm and they were just fine.
The tires I have now were chosen because of cost and because I talked to someone else that had them already and liked them.
With respect to airing down, I run about 12 psi on a trail, 18 or so for exploring rough gravel roads, and about 30 on the street. You should be adjust ing pressure to suit where you are going – it effectively adds a couple more inches of travel, softens the ride and increases grip.