Kefka is on the right track. There's all sorts of computer repair sets you can find. Head over to newegg.com and just search "tool kit" and you'll get tons of results. I can't imagine one being better than the other, and unless your boy KNOWS he needs X and thus you should LOOK for X, it probably won't matter which one you get. Just get a middle-of-the-road not-too-expensive set.
Really you need - at the least - a decent tool set with full sized implements (screw drivers) as well as miniature versions of the same (for small parts and precision tasks). Additionally I'd suggest a good pair of scissors, since those are always useful. Cans of compressed air are always good, or perhaps some kind of tiny vacuum that can be used specifically for clearing out dust.
If he's technically inclined, you can get a nice solder set, but I wouldn't know anything about that (need to learn how).
Thumbscrews and plenty of 'em.
You can always pimp him out with sets of various cables for installing/removing different components. I personally like to keep cables from outdated things as well, such as old parallel printer cables, since sometimes I have to help people with those.
A large sized USB drive is always good - I keep one FULL of all the programs I have downloaded in case I need to reformat a computer or work on someone's.
If he makes LAN cables, you can get him a set like this. Highly useful for all PC nerds. Making any length cables for LAN parties or general networking is always a good skill. Having a cable tester is good just to have since you never know when the stuff someone is using might be faulty.
Hmmm what else. Tools, compressed air, extra internal cables, scissors, thumbscrews, USB drive, LAN equipment...maybe a good amount of CDRs/DVDRs/DVDRWs since those are always useful.
Those are the things I keep in good supply for any and all endeavors. Hope this helps.
