Mega Man 8-Bit Deathmatch, both single player and multiplayer, along with some mods of the base game called Competitive Class-Based Modification. Basically, it turns the core game into what I could best describe as a hybrid of Team Fortress 2 and Overwatch to a degree. Keep this in mind, as the characters you play as aren't just skins when you start up into a server. No. They have their actual character specific movesets from the Mega Man games. Might need a bit of rebinding the keys from time to time, but otherwise, I've enjoyed this mod to a degree, even if nine times out of ten, I end up getting my ass kicked.
And even though the PlayStation 3 servers have all shut down, I still find myself going back to games from the last few console generations, especially stuff I got from the PlayStation store when it was still active. No knowing if for sure if the store is still active there, but perhaps there'll be time to test that thesis out. Still have Klonoa: Door To Phantomile, the original Tomb Raider trilogy - though I gravitate more towards the second entry - and Daytona USA, not in that order. With Daytona USA though, I stopped after a few years before jumping into it again just to finish up what few challenges there were left as well as attempt to finish a Survival mode run.
For the Wii U, I mostly run it as an emulation box through a website exploit before booting up RetroArch. Don't need much else going into that.
For my XBOX One... Uhhhhhhhhhhhhhhhhhhhh...
Otherwise, I've also partaken in a few others like the Viscerafest demo which is basically if Doom and Metroid came together what popped out could be an absolutely adorable baby... But then half of the baby's face looks like an Eldritch abomination that then grows up to becoming a bloodthirsty, egomaniacal and morally ambiguous psychopath who lifts occasional one liners from Blood and POSTAL. Like seriously, what the absolute fuck happened with this girl's face? But that's what happens when you decide to stick your dick in crazy, jus' sayin'.
Then I grabbed the ULTRAKILL demo. Oh boy. Anything I say about this game would be considered a spoiler, but if you want a taste of the otherwise batshit craziness you're gonna experience, get the demo first and if you love the Devil May Cry combo system along with your Quake inspired gameplay and you like the sick tricks you can pull off with your guns, then you will LOVE this one.