The Waco
The most common Waco used for wingwalking was the UPF-7.
The WACO UPF-7 1937, 1938, 1939.

Empty weight: 1,870 lbs
Gross weight:  2,650 lbs
Service ceiling:  18,500 feet
Cruise speed:  145 mph
Top speed: 133 mph
Wing span: 30 feet.
Length:  23' 1"
Height:  8' 5"

Waco is the famous acronym for the Weaver Aircraft Company. 
It was founded in 1920 in Lorain, Ohio, by George "Buck" Weaver,  Elwood "San" Junkin, Clayton "Clayt" Bruckner and Charles "Charlie" William Meyers.
Sam Junkin, a draftsman at several airplane companies including the Curtis Aircraft company, and his Childhood friend Clayt Bunker, a assembly foreman at aircraft plants, designed a plane on floats.  Buck Weaver, a barnstorming pilot and flight instructor, and Charlie Meyers were also designing a plane and the four teamed up together.  Their first design was the "Waco Cootie" a mono-plane.  It crashed on it's test flight leaving Buck Weaver with many injuries.
Undaunted the team continued to design even as Buck healed and their next plane the WACO 4, a bi-plane for three people, was more successful. 
Thus began a long successful history of affordable easy to fly family oriented aircraft.
The first 10 models were number one through ten.  After that there was a complicated three letter system.  The first letter stood for the type engine used, the second letter for the wing design and the third letter for airframe.
Perhaps the most unusual application of this wonderful aircraft was by Jim Franklin.  He designed what he called a "Mysteryship."  He would often put on two acts with it including a wingwalk act.  Then he went on to outdo himself by engineering a jet engine for another Waco aircraft of his.  It was an amazing act.  You would hear the roar of a jet and here comes a bi-plane, literally a blast from the past.  His son, Kyle, continues flying the Waco "Mysteryship" in airshows as part of the Sons of Legends.
Today the company is owned by Neil Whittlesey, but everyone that owns a Waco has pride in their rare aircraft and they know they own and fly a symbol of the Golden Age of Flying.