This remains a staple for SteamVR users. It allows you to manually offset your playspace, letting you reach items or move "through" walls even if your physical room is small.
While not technically "mods," the community has documented "hot" experimental combinations in the game’s that act like hidden content: rick and morty virtual rickality mods hot
A fan-favorite "mod-like" secret where combining a mega seed with a jar of goo (and a few other morbid steps) creates the iconic character. This remains a staple for SteamVR users