This activity is great for fostering and recognizing team work.
I have done it as an opening or a closing activity. 
It is called the token of appreciation. Here is how it works:
  1. Bring a chocolate box to the retrospective
  2. Ask people to form a circle.
  3. You can start as a facilitator by saying: “I would like to give a chocolate for Paulo in recognition of that time when he helped me with…
  4. Then you give the chocolate box to Paulo and ask him to repeat the gesture.

Below are two photos from this activity when used on a large group retrospective.

 

AgileBR-tokenOfAppreciation2

A large group formed a circle for the Token of Appreciation activity

chocolate exchange as a token of appreciation

chocolate exchange as a token of appreciation