Since everyone is sharing their gamemodes, here is mine that blows away any competition for years to come. This gamemode is called Shitters.
Shitters is a short round-based gamemode of shitting all over the floor and not slipping on it while you compete against other players also shitting on the floor. You step on shit, you slip and die.
It plays a lot like slitherio when viewed from a top-down perspective.
You are constantly moving and shitting, it is third-person and all you can do in terms of movement is turn around with your mouse. You can hold right-click to hold in your shit for up to 5 seconds, the more you hold in the further your shit will hit (projectile shitting) when you release your mouse.
Here is a quick preview of what the player should look like in-game.
This gamemode will mainly be for me to just learn gamemode development for the game. Seeming as it’s a simple enough gamemode I plan to have a playable version about 1 or 2 weeks after I get my hands on the game.