Team members write appreciative postcards for later delivery Source: Philip Rogers
Hand out blank postcards. Each team member silently writes a postcard to another team member, thanking them for something they did. They can write as many postcards as they like, and they can address them either to individuals or to multiple people. Collect all postcards. Consider using envelopes with the name on for privacy. Deliver the cards throughout the next iteration to make someone's day.
Variation: Use normal paper and let participants fold the paper into little cranes for some origami fun. (Suggestion by Virginia Brassesco)