A Riddle Game
This will be a riddle game in the style of (or as close as we can get to) the famous riddle game between Gollum and Bilbo - except that we only play for the fun of it.
The one who finds the answer gets to post the next riddle.
If there has been no anwer for ten days everyone is invited to simply post a new riddle.
(in all liklihood) Your mom has at least one,
Your dad has one,
You probably have at least one;
Your eyes have them on bad days;
Your ears might have them on any day;
Middle-earth has at least twenty-one of them;
And Saturn has lots and lots.
What am I?