If I wanted the repaired joint to be as invisible as possible, I'd use white wood glue, like Elmer's or Weldbond. The advantage of white wood glues is that they dry clear, and that makes for the most invisible repairs. Clamp the joint tight, wipe up any white wood glue that oozes out of the joint with a damp rag or sponge, and allow to cure.

If I wanted the strongest repair I could get, I would use LePage's PL Premium construction adhesive. PL Premium now also comes in a high tack variety that gives a better initial grab, but you still want to clamp the joint tight as it cures. PL Premium is a moisture cure polyurethane, and because there's always some moisture in wood, it works particularily well on wood. To store a partially used tube of PL Premium, just squeeze a little out so that you can grab onto something, and store it in your freezer. When you want to use it again, take it out of the freezer, put it in your caulking gun and apply pressure to it. Then pull out the cured stuff at the end, and it should start to flow again, but very slowly. Allow time for it to warm up, and it should be ready to use again.