Consider a knife between 4 and 5 inch blade. A Frost's Mora is a great field knife. The blade size depends on the model. It can do batoning, sharpen sticks, field dress game, and kitchen chores.
Also really easy to sharpen, no special skills required. Just a good stone and a few minutes time.
They do not look like a "Rambo" knife or a Darth Vadar commando knife, they just do the job and cost under $15!