Pokemon Auto Chess. Literally what the name implies, a Pokemon auto battler fan game. Honestly it's really well-polished for something only a couple of people are working on (aside from commissioned sprite artists) and has an active community to go with it.
Gaming
From video gaming to card games and stuff in between, if it's gaming you can probably discuss it here!
Please Note: Gaming memes are permitted to be posted on Meme Mondays, but will otherwise be removed in an effort to allow other discussions to take place.
See also Gaming's sister community Tabletop Gaming.
This community's icon was made by Aaron Schneider, under the CC-BY-NC-SA 4.0 license.
Hedgewars - it's like Worms Armageddon, but probably even better. I wish more people played online though.
[https://spacestation14.io/](Space Station 14)
Aside from the other choices already mentioned (especially Doom stuff, FreeDoom ftw) any of the free games derived from the S.T.A.L.K.E.R. games and early builds, mostly Anomaly and Lost Alpha. There are also a few stabilized versions of the Build 1935 alpha out there which are worth playing and probably a bit more approachable for most people.
Technically not the whole game, but Smash Remix is an open source rom hack of the original Super Smash Bros. for the Nintendo 64. It's been a blast from the past and I'm enjoying the hell out of it.
I also love the fact that a lot of N64 emulators are open source too, like Mupen64 or simple64
I made one! It's a solitaire-like but with some new mechanics, and fairly polished and balanced at this point. You can find it on itch and on the play store. Here's the source.
Not really, but kid has been happy with gcompris
I've had a ton of fun in Red Eclipse over the years.
Openttd