Agree. I would also choose something that has ammo that is relatively easy to find and relatively inexpensive for the kill power and range that I wanted. I would probably get something supressor ready as well. Hogs are a major problem in Texas, though, so I'm a lot less concerned about typical long range hunting concerns than I am with dealing with the quantity.You seem to be asking about two different things from the thread title and how you want to use it.
So you want a truck/4 wheeler rifle? I think your best option would be a shorter barreled bolt action, say 16" and in a goodly sized caliber such as .308. The reason why I am suggesting a bolt gun is that truck guns tend to end up being a bit neglected and a bolt gun isn't nearly as dependent on proper lubrication or suffering from a dirty action than semi-autos. So it will be more reliable under worse circumstances, which is a good thing. It will also tend to be a less expensive option. With a polymer stock and short barrel, it will tend to be very light and handy as well.