A little ribbon and a couple of hooks and these lamp prisms from the flea market make fantastic Christmas tree ornaments. They really reflect the tree lights too! I found quite a few prisms in ruby, amber, cobalt blue, and clear colors, also in a variety of shapes.
Vintage cookie cutters in holiday shapes such as trees, stars, bells, reindeer, and gingerbread men and women also make great ornaments, with a little ribbon to hang them on a tree.
I also found some vintage keys at a flea market that make simple ornaments too.
Just the other day, I thought of hanging colored glass swizzle sticks on the Christmas tree too! I love colored glass, especially when it reflects the light. I used a little floral wire to wrap around the top of the swizzle stick and then form a loop above it where the hook can be attached.
I am sure there are quite a number of other vintage items that would also make fantastic Christmas tree ornaments. Please comment to let me know how you have used vintage items in your holiday decorating!