CRAWL (pseudo co-op / vs mixture)
Lovers in a Dangerous Spacetime
Wizard of Legend
System Shock 2
Monaco: What's Yours is Mine
Pixeljunk Shooter Deluxe
Sundered (I haven't tried it yet in co-op, but they added it. Love the game in general.)
No Man's Sky
I don't have it yet, but River City Girls looks fun.
Thanks for the reccomendations! It was a bit to broad.
I am looking to get a friend into gaming. They only have a macbook at the moment. I will have a PC. Not really interested in any battle royale type games or MMORPGs. Looking for something fun to play that doest necessarliy require a huge time commitment and can be played pretty cassually.
I would hop on Steam, and filter by Mac and co-op. That would give you a pretty good start. Borderlands runs on the Mac, so there's one thing. It's a shooter and action RPG, but on the "lite"er side of both genres. It's easy to get into, and pretty addictive. Could be just the thing.
Monaco is a ton of fun. It's a heist game with multiple classes. You break into places and steal things. Each character can do different types of things. Hacking, breaking through walls, crawling through vents, distraction, etc. It's overhead, and very easy to get into, and controls are easy and transparent.
Actually, my brother and I have been on a new kick lately. We drink a nice whiskey and play old golf games. Everything from Power Golf on the TurboGrafx up through the newest Mario Golf, and everything in between. (Neo Geo has some good ones.) Even if golf makes you want to vomit, playing video-game-golf with some alcohol is fun as hell.
Also, Light Cycle matches on Tron 2.0 are fun. (I doubt the Mac is supported though...)