I have a '01 sr5 Sports Edition. Its the 1st year with the hood scoop and its chassis is far better looking than the redesign that occured in '03 IMO. Straight from the factory the engine is a bit underpowered on acceleration, but fine on torque. It really is a truck, which i love in the days of unibody pseudo cars posing as trucks, SUVs, and 'sports utility wagons'. It was (and i think still is) the only truck with a locking rear differential straight out of the factory, meaning you can drive off the showroom floor and on to the trails without any other alterations.
I've had a wonderful experiance with my vehicle and have had a terribly fun time in 4x4 mode. The newer ones have a beefier engine, but i'd go with an '02 sports, since it has a better skid plate from the factory. If you want a toy for crawling and pure offroad, look for older models, much like the one pictured a couple posts above. Get a "6 suspension, "35 Mud terrains, Dana 44 locker...and you're in heaven.