Handy, small things make awesome gifts. Stuff that they can add to their everyday carry. A nice pen, like a Fisher Space Pen, that fits well in the pocket or a Gerber Shard to add to a keychain. Any little trinket type item that can serve a purpose, while still looking cool.
Something a little more pricey, but an even better gift, is a good pocket knife or multi-tool. I carry one on me constantly and it's saved my butt over and over again. Plus, it's sturdy enough to use as a pry-bar to get things open if it can't cut it.