We got this idea from Moore N Moore Sporting Clays shooting range. It's a great way to repurpose plastic shells you aren't going to or are unable to reload.
- 1 string multi-colored or white Christmas lights (the small kind)
- About 50 shells of multiple colors (20-12 gauge work best, 28 gauge may be too narrow)
- Hot glue gun with a good number of glue sticks (6-10)
- Soap and water
Basically what you do is you collect a bunch of shells, and give them a good washing in hot soapy water since they'll have powder all over them.
You can separate them by color so you can figure out some kind of pattern that pleases you. Or just go random if you aren't that anal.
Finally, hot glue the open end of the shells to your string of lights. You may need pliers to smush the open end a bit closed so that it makes better contact with the light string. But we just glued the edges of the shell to the wiring and so far, after two years, they've stayed intact.
Psst: For you non-DIY types, you could always buy them on Amazon.