A shiny ball hung on a Christmas tree as decoration.
Dobby hung a bauble on a loop on the top of his tea cozy on Christmas, 1994 (GF23).
Dobby decorated the Room of Requirement with a string of a hundred golden baubles with Harry's face on them and the words "HAVE A VERY HARRY CHRISTMAS!" (OP21). Later Harry dreamed that he was putting up baubles in the shape of Dobby's head (OP23).
Glowing Christmas baubles were used to provide lighting at St Mungo's during the holidays instead of the usual crystal orbs (OP23).