Picks are a personal thing.... you can get them made out of all sorts of things in all sorts of thicknesses and shapes.

They are also fairly fragile, so if you're thinking about that, it might be worth getting a metal one and having it engraved. If you buy plastic and he uses it, it won't last long....

I've seen silver ones about that are pretty cool. You can get them made into jewellery too... not sure about that myself, but hey.... it's an option...