I don't really have a favorite, but boy my husband does.
He LOVES the Hallmark Muppet's ornament of the old men from a couple of years ago. I bought it in Oct of the year it came out, and he played with it so much before the tree was even out--so as a safety measure I bought a second to have if it broke. Well I find out later that he too bought an extra. So our tree has one, and two in reserve. He has replaced the batteries in the one on the tree a couple of times.
Every time he walks near the tree, I can hear the old guys talking.
Before that ornament, he could have cared less about the Christmas tree, now he would put it up in Oct if I would let him.