The Finals changed some in-game props into jack o lanterns you can throw at opponents to deal damage, and the maps have a spooky variant with spiderwebs and whatnot.
Phasmophobia is running a Halloween event amidst its console release, but it's mostly just playing the map to make a counter go up, kind of disappointed.
Deep Rock Galactic has the usual lobby reskin, and extra cosmetics, always fun to go back to !
I found the changed atmosphere of the maps in the Phasmo event to be quite spooky. Plus, I can't confirm, but the ghosts felt like they were acting strange...
Dead by Daylight added mystical smoke grenades survivors can use that are a lot of fun - many are suggesting it might become an ability as part of the main game.