I wouldn't know where to start but a robot that could interact with Autistic children, play games with them, use text to speech to tell them stories and help teach social skills would be a fun robot to build.
By Lemon
Other robots from Synthiam community

Ezang's Two Projects From The Past - Re-Mixed
2 projects from the past by Justin - re-mixed - Detecting face or does not recognize a face - Activating a robot sound...

Jstarne1's Meet Squeegee , The Flooring Mopping Robot ,...
This is a simple project that hopefully I wont over complicate. Since he Squeegee needs to get as close to furniture and...

DJ's Vision Tracking Robot
This is a test robot DJ Sures created to trial a new module that he has been working on. It tracks and follows objects...