Rohit Pardasani just announced a new XMPP-powered game called Tankaar. Tankaar is a peer-to-peer artillery game similar to Worms or the old QBasic classic, Gorillas. It has an integrated messaging client, and both the messaging client and the game use XMPP for communication.
I've long been a huge fan of using XMPP in the gaming space, so it pleases me greatly to see more people working in this area. The built in social features of XMPP are a perfect fit for multi-player games.
Tankaar is written in Java and uses the Smack library. It is designed to be platform independent, but it appears that only a Windows version is currently available for download.
I'll be e-mailing Rohit to see if he's interested in participating in the XMPP case studies interviews.