Medieval II is my Total War of choice. I'm anxious to buy Warhammer II, but I think I'll pass until I can buy it with all the DLC. I'm not sure how many players Wazhack supports, but that's also a fun game and I'll re-buy it on PC if you all will.
Saints Row IV is allegedly multiplayer, but I usually prefer to play stuff like that on my own. Though, I hear Saints Row II is one of the best multiplayer games ever made... And, again, I'll buy that if everyone else does, even though that's probably also maybe 2 at a time.
Apparently there's a functional mod for multiplayer in Fallout New Vegas. I was meaning to install that a long time ago but I remembered I'm shit at installing mods without Nexus so I never looked for it.
I'd also be willing to play a round of CYS TF2, but it has to be on the Wacky Races map or whatever that game mode was where you had to push your full-sized van/spawn to the end before the other guys.