Cell Block A

Cell Block A is a competitive two player local combat platformer set in a prison that operates by death sport rules. It looks like it was programmed in an afternoon, but it plays like it was iterated and playtested for at least a year before release.
Both players have hit points that can be worn down by attacks, but there are also a plethora of one-hit-kills. Weapons of increasing utility fall into the screen at irregular intervals. When a player character dies everything resets, until one player has lost their last life, at which point their opponent is declared the victor.
The beauty of Cell Block A is in how varied the tactical options are. Rolling into an opponent throws them behind you - you can use that to toss them into the insta-kill pit below. Touching a ducking character throws you behind THEM, which takes priority, so they can counter you. Landing on an unducked character from a fall of at least one level snaps their neck for an instant kill. If the round goes on for a bit, shotguns start getting tossed in, which kill in one shot if the characters are on the same platform level. Fire extinguishers have a limited short range freeze ability, or can be used as bludgeons that deal more damage than normal punches.
All this combines into a quick, violent game with rapidly changing tactical options and character advantages. Maybe you have a shotgun, so I make a hail mary drive at you from a floor above, but you duck in time to throw me to the edge of the pit. I turn and spray you with CO2, my last shot of it, the moment before you can pull the trigger. I dive for your legs in a roll, throwing you to the edge - do I hurl myself at your chest, hoping to push you in, or do I scramble for the nearby ladder, hoping you'll waste your last shot in a near miss? Lots and lots of emergent gameplay and wild swings of fate from very simple NES-level controls.