Everybody sums up the last iteration in 3 words Source:
Ask everyone to describe the last iteration with just 3 words. Give them a minute to come up with something, then go around the team. This helps people recall the last iteration so that they have some ground to start from.
Walk through each story handled by the team and look for possible improvements Source:
Preparation: Collect all stories handled during the iteration and bring them along to the retrospective. In a group (10 people max.) read out each story. For each one discuss whether it went well or not. If it went well, capture why. If not discuss what you could do differently in the future. Variants: You can use this for support tickets, bugs or any combination of work done by the team.
Asking and answering go around the team circle - an excellent way to reach consensus Source:
Everyone sits in a circle. Begin by stating that you'll go round asking questions to find out what you want to do as a group. You start by asking your neighbor the first question, e.g. 'What is the most important thing we should start in the next iteration?' Your neighbor answers and asks her neighbor a related question. Stop when consensus emerges or the time is up. Go around at least once, so that everybody is heard!
Team members write appreciative postcards for later delivery Source:
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)