I've played a lot of Left 4 Dead 2 with friends throughout the years. We've recently spent another couple of weeks running a map or two every night. Feel free to send me an invite if you want to join when we have an open slot.
I also wanted to recommend No More Room in Hell. I remember checking it out around 2013, but there are a lot more maps than I remember, and I've been enjoying it quite a bit. It's sort of like a slower-paced Left 4 Dead. Ammo is scarce. Zombies are slow, with occasional runners. You can become infected, requiring medication to hold it off, or else you'll turn. Most of the maps have a variety of paths, objectives, and even escape scenarios that are randomized.