Hmmmm... Sport plane to me means able to be utilized in a vast number of arenas or posessing qualities observed over several classes of aircraft. Having said that I will differ to my first kit after my trainer - an Easy Sport 40. Absolutely fantastic characteristics. I'm suprised I haven't seen it mentioned yet... that I can recall.
Another excellent 'sport utility' plane was Hangar 9's Advance 40. Now that plane could take some serious abuse and knife-edge at the same time. Flat spin easily and land like a feather.

Sticking with what has been mentioned so far, I'd say the Kaos is probably the most widely recognized sport-type plane.