QWOP

QWOP is an esolang by User:Rdococ. As the name suggests, it uses four characters: Q, W, O and P. All others are ignored....well, except when following the letters W and P.

Overview
Q is a quine. Here is the shortest non-null quine: Q

W is a conditional. If the input character is not equal to the next character, it will skip the next command: Wxy

O is a loop. It will return the pointer to the last O, if one exists. Here is an infinite loop: OO

P is a print command. It will print the next character rather than executing it: Px

Hello, world!
PHPePlPlPoP PWPoPrPlPdP!

Quine
Q

Truth-machine
OW1P1W1OW0P0

Computational Class
I do not have any formal proof, but I have settled on the educational guess that QWOP is a bounded storage machine with bounded input. It's clearly not TC, and the input is restricted to one character.