I don't have a truck. But the knife I keep in the OOPS compartment of the car along with the spare tire, tire iron, jack, pliers, screwdriver and cheater bar, is a Cold Steel Pocket Bushman.
A fairly indestructible knife with a bombproof lock, a tough generic 4 1/2-inch flat ground stainless blade which can be used for many different chores... and inexpensive.
Like the other things in the OOPS compartment of the car, the likihood of use is fairly low.
Note: the "cheater bar" is an 18" piece of water pipe, because the tire iron supplied with cars as standard equipment these days is too short to reliably remove the lug nuts.