Mostly endless, quite possibly story-less games. Played this sort of stuff a lot more in the past, nowadays either when I'm too tired for anything else, or I'm on a playthrough.
Some cool endless games I can personally recommend include:
Deep Rock Galactic *
Monster Hunter (up to 4U; playthrough-friendly) *
Bloons TD 6 *
Cataclysm: Dark Days Ahead (playthrough-friendly)
Trackmania (competitive, indirectly) *
Animal Crossing (up to New Leaf; playthrough-friendly)
Team Fortress 2 Classified (formerly Classic)
ArmA 3
Left 4 Dead (2) (playthrough-friendly)
Space Station 13
Club Penguin
Stardew Valley (playthrough-friendly)
Fallen London (playthrough-based, continual updates)
Minecraft
* = currently playing, more or less