A wallflip (or Wall Backflip) is a backtuck done with one step on a wall or a tree.
Invented by Chase Armitage.
Wall Double Fulltwist
Ben "Jenx" Jenkins was the first one to do it on concrete and off one step.
Skynative was the first to land it on a slanted wall on mats, but has not yet attempted it on a flat wall or outside.
It was attempted outside here with the aid of spotters, but was bailed: 
It was also done here in a gym with the aid of a spotter and a large crashmat: