Not knowing what he already has makes it a little difficult.
Thinks I would like would be an assortment of quality terminal tackle: hooks, different styles of swivels, weights, leader. Those are the things you can't have enough of.
A nice fillet knife always comes in handy. I love a good pair if needle nose pliers that have a split ring opener on the. Depending on the species, a Bogo Grip with a built in scale would be nice.
You didn't mention what he fishes for or the techniques used. If you add more info, I would surely be able to give you more suggestions.