Many magic rings... with strange powers!

[the guy who be short]

Remember this line:

There are many magic rings in this world, Bilbo Baggins, and none of them should be used lightly.

(I'll admit, it's a movie quote.)

Well, what strange powers would these other magic rings have? And so that this doesnt become a list thread and something for BW to take his anger out on, instead of just writing it, add it into a scene.
E.g:

Gandalf: There are many magic rings in this world, and none of them should be used lightly. Oh, except this one.
(produces a ring)
Bilbo: Oooh... what does it do?
Gandalf (handing him the ring): Try it on and find out.
Bilbo: Thanks. (Puts on ring and promptly turns into a frog)
(Gandalf rolls on the floor, laughing his beard off)
Bilbo (froggy voice): haha, very funny.

Ok, im sure you peole can think of better ones. And two things: 1) i dont think the BW would appreciate rings that... er... control certain bodily functions. 2) Please read what other people have put first, because i really hate it when people repeat stuff already said.

Let us begin!