Half Dead 2 is a multiplayer version of the movie Cube. A group of players are trapped in a grid of cube-shaped rooms, searching for exits while avoiding death by impalement, fire, laser amputation, freezing, and robot-caterpillar-things. It's $5 on Steam and it's not going to win any awards, but I'm always down to play.
Half Dead 2 represents a growing category of games I love: Cheap multiplayer nonsense that's good for a laugh more than anything. You might call them party games, but that brings Wii minigames to mind for me. These aren't games of any particular genre, but they share a few traits. They have online multiplayer support, they're cheap enough that everyone in a given Discord server is willing to give them a try without really caring if they're good or bad, and they're built well enough that they're genuinely fun, or at least funny.
Another game in this category is Golf With Your Friends, which is $6, buggy, and always fun, especially when you pick ridiculous Steam Workshop maps. And as a more stylish example, there's Regular Human Basketball, which takes some practice to figure out, but is hilarious once you do. It's also $6 on Steam.
It's more than just having online multiplayer and being cheap that puts a game in this category. Qualifying games should also be fun for just about anyone. If being bad at them is funny rather than frustrating, that's ideal. One of my favorite games, Ratz Instagib, doesn't quite fit, because ultra-fast hitscan sniping wouldn't be much fun for someone who's new to shooters. Shotgun Farmers, on the other hand, is good for a laugh even from last place.
The last thing that binds these games is that you need a group of friends willing to try them. Searching for an online match by yourself will often be fruitless, and even if there is an active playerbase, some games just aren't fun unless you're in a voice channel with people you know.
Discovering games that are actually worth a group session requires some trial-and-error, most of which is done for me by generous Discord pioneers (every game I recommend here was recommended to me by someone else first). Many of these games live on the border between being funny and being jokes—games with comedic premises that aren't actually fun to play—and you've just got to give them a go to find out which they are.
There are a few reasons these games are flourishing right now. It helps that Steam is open to many more developers than it used to be, but that wouldn't matter much if game development itself hadn't become much more accessible. Unity and Unreal have contributed in particular. A lot of opportunistic crap ends up on Steam because of all this, but also plenty of genuine efforts to discover. Hunting for games to share is part of the fun of Steam.
What I like most about these games is that they aren't hoping to be the next big games-as-a-service hit. They're comfortable in their niches, and playing them doesn't feel like becoming part of a 'community.' There's no commitment, no coercion to get invested. Where Apex Legends and the like are public squares, these games are the private hangout spots hidden among back alleys.