Jim Bonacci's "GameTest12" (found online demo fighting game; 2006)
Internet game designer Jim Bonacci is usually recognized for his highly popular online game Happy Wheels, but before he began development on that game, he was actually trying to create a Street Fighter-esque game only known as Gametest12.
The game consisted of two players (taken from Jim's earlier flash animations) in an art style similar to Happy Wheels, but are much more early and rough. Player one could perform many finishing moves which were listed to the side of the screen, all of which involved pressing a lot of buttons and were very hard to pull off. Additionally, pressing two specific keys gave the player a knife and baseball bat to fight their opponent with. These both performed instant kills (lodging in your opponent's forehead and crushing their head, respectively). Despite the violent nature of the game, it wasn't nearly as violent as other games of the type due to its simplistic cartoon style and unfinished nature.
The game was uploaded to the site as a link and stayed there unlisted for 7 whole years before being removed in late 2013. On June 1, 2016, however, the game was found via the Internet Archive and is available for play