What would you do if somone took credit for your work?

I guess I would be slightly annoyed if someone took credit for something that I created, did or said. Any action that I might take would definitely depend on what it was and how important it was to me, or if it could possibly negatively affect my life in anyway that I might not appreciate. If someone that I worked with intentionally stole my idea or took credit for my work it would upset me. But, I feel that a person who do this type of thing has no morals, values or integrity, and will eventually get their just reward.