I'm surprised no one has mentioned the Aircoupe -- sort of the Volkswagen of aviation. Have a look at it here .
Almost every one of them I ever saw was just unpainted aluminum, rather than the gussied up version shown.
There were also some Beechcraft planes — twin-engine, twin-tailed — that carried about 10 or 12 passengers. I don't remember the nomenclature, but there was a military version of it as well, mostly used for generals to get around.
I'd second the Stearman suggestions — great aircraft. Big nine-cylinder radial Lycoming engine, bi-wing, very aerobatic. I once rode in the dusting hopper of one that had been a crop duster. Scary ride.
Other notables included the de Havilland Moth, which was around in various editions from the mid 1920s to the early '50s.
And who could ignore the Douglas DC-3, the plane that virtually invented commercial aviation. It's military version was the C-47, a workhouse that was still used by the USAF till the late '60s.
If you want specifics on any of these, send me a PM and I can get specs for you.