the People's Champ said:
depends on what you want the truck to do. rock crawling? go with a shorter wheelbase vehicle like a jeep
mud bogging? full size pickup with some fattie tires
prerunner? minitruck with long wheel travel suspension.
Couldn't of said it better myself.
Although, my favorite off road vehicle would be the Toyota Tacoma, it's lightweight, and comes with a 3 inch higher suspension than anything in it's class or full size class. The older models also have locking differentials, so if you start slipping backwards your four wheel drive wont disengage.
The new Jeep Liberty is also really enginereed well, it too has rear locking differentials, which allow you to have select tires on the ground and the truck won't slip, because it has selective tires movement.
You could always press your luck with a Hummer, they have CTIS, and a locking differential on every tire (nothing else has this), and a nice ground clearance. Tons of power, great dimensions as far as wheelbase and distance goes, but they also cost over one tenth of a million dollars. They also wiegh alot, so depending on what kind of terrain you are in you might find yourself using the built in wench way too much.
Really, just get whatever you can afford, and spend all the rest of your money on the best off roading tires you can find, that's the key, it's all about the tires.