Just wanted to point out to everyone that Steam's annual Summer Sale is coming up!
I would keep my eye on Ace Combat: Assault Horizon. It should get really cheap during the sale (do remember, don't buy anything unless it's on a Flash Sale, Daily Sale, or it's the last day), and after the sale I'm definitely going to host at least one multiplayer match in Assault Horizon for our Steam group!
I'd also like to point out that Tom Clancy's H.A.W.X. would not be a bad choice either. While it is hampered by a lot of Ubisoft's poor coding, especially when it comes to multiplayer, what I played of it was a ton of fun especially with others. HAWX has gotten really cheap in the past, and Ubisoft will definitely have a day dedicated to them or something, so I'd definitely suggest keeping an eye out for that. Apparently, though, HAWX 2 was a horrible game that shouldn't even be mentioned, so beware about that one.
Good luck to everyone who's trying to hold onto their wallets during the sale! :)