I second the Avistar. If you learn fairly quickly, you'll like the extra capability the Avistar has over the PT-40 or other flat bottom wing trainers.

The Avistar is just a little faster, tracks better and is less "floaty" than the flat wing trainers. It handles the wind better and can do basic acrobatics - inverted, rolls, loops, hammerheads, etc.

Sure - trainers are not sport planes, but they still can do some cool tricks. Someone can learn easily on the Avistar and once they learn, can still get a kick out of the flying it regularly.