This necklace takes a matter of minutes to make but is so fun because it can be customize in so many different ways. It's probably easy enough to figure out how to make this without me showing you so I hope this serves more as an idea to expand upon. Check out the last step to see some variations I cam up with.
To make a Lego Dangly Necklace, you'll need:
-1x1s with the tubey things on the end
-string or cord
-bricks to decorate with such as 1x2 or 1x4 plates or studs
String the cord through the tubey end of the plates, making sure they all face the same way. Tie the two ends of the cord together and you now have the base of the necklace.
The picture show some ideas but you can go wild with colors and arrangements. Enjoy :)