So, every now and then, not the main actors, but an actor in a relatively smaller role is so good they steal either a scene, or a sequence, or even an entire movie.

In your opinions, what are good examples of these.

A couple of the top of my head:

The character Kid Blue in Looper. Although he seems to be considered stupid in the film by most of the other characters, he really seems to keep getting ahead and outsmarting others (although he always ends up screwing it up again).

Bill Murray in a very small role in Little Shops of Horrors. Steve Martin is the lunatic dentist who likes to scare and cause pain in his patients, but then out of nowhere, Bill Murray comes in and totally flips things on their head. He enjoys pain and wants the dentist to do his worst.

I know I have a lot more examples, I just can't think of them at the moment. If I do, I'll add them to the list, but I would like to hear about your own.

EDIT:

Some good answers, but some people clearly don't even understand the question.

EDIT:

How in the hell did this post blow up so much?

EDIT:

I just remembered a good one. The character of Ellis in the first Die Hard movie.