Finding the right glue can be tricky. Epoxies can be a mess. Specialized adhesives can get expensive. Hot glue = ick.
I recently found a glue that I can reach for in most situations — Gorilla Glue. This solvent-free polyurethane glue is best on wood (sands well), but it’s not as specific as most wood adhesives. It bonds pretty well on metals, stone, ceramics, and many plastics. Another nice thing is that it foams up a bit when you apply it, so a little bit goes a long way and you don’t need to spread it around so much. It is waterproof, meaning it doesn’t break down when wet, and doesn’t expand or contract with temperature. You do have to clamp stuff in place for a while while it dries, which you should do with any glue. If you glue infrequently, it is nice that Gorilla Glue has a long shelf life — three years as opposed to one, as with many other polyurethane glues.