The title I'm using was the title of an email I received on one internal mailing list. It was about a team where they tried to get more focus on completing stories. Also known as reducing cycle time, i.e. the time it takes from a story is started until it is completed. Anyway. The team was opposed to more statistics and graphs so this one guy came up with the idea of using smilies. The background is that this team wanted to complete all stories within three days. So when a story was started it got a happy face. On the second day it got a flat face and on the third day an unhappy face. If a story takes longer it gets an angry face (different levels of anger for each day going forward). Whenever a story is completed it keeps its face but also get a happy face with a trophy.

So did this work? Apparently it worked very well. In the daily stand-up meeting it is now common to hear things like "No you must help us complete this story so we don't get an unhappy face" when somebody indicates they will pick up new work. I think that is exactly the behavior you want. I might have to steal this idea...