SEE YOU SPACE COWBOY abbreviated CUSC is a ruleslite cowboy beepboop game. It's easy to run and pretty improv heavy so I could run it on short notice. It is incredibly beginner and oneshot friendly. Crawl is an in-developement game from the same developer that uses the same basic engine for old-school dungeon-crawling, currently Patreon only.
THe 1977 Holmes edition of D&D is the so-easy-a-caveman-can-do-it version. Blueholme is a modern clone that expands Holmes for high-level play. The original also comes with a dungeon, and Blueholme has a module that serves as an expanded version of that too.
The world's favorite Teen Titans simulator. There are a few more moving parts to this one than the other two but once you get the hang of them it absolutely nails the vibe. Based on the Apocalypse World engine ("PbtA").
Another rules-lite game similar to CUSC for Metal Gear-type action. Irregular is a hack to make it about sad robots.
Sci-Fi Fridays circa 2000 simulator. PbtA like Masks, and still in beta but it already looks pretty darn good.
Space train space game based on the Blades in the Dark engine ("FitD"). Meant for oneshots and looks pretty nutty in a good way.
PbtA fantasy mech game?
The first is a PbtA Team Rocket game, and the second is in beta taking the same system and breaking it out into a full fledged Pokemon game.
PbtA monster hunting game, one of the early genre codifiers and very well-regarded.
Man I Love Fishing