I'm sure there's one floating around here, but I couldn't find it. Throw down your ideas for This Is the Run.
I propose Zombies Ate My Neighbors, a 90's classic. It's difficult, huge enemy variety, great weapon variety, marvelous opportunities for Vinny and Dan to mess each other up, and great maps. It's a longer game, but the passwords to get to different levels would allow them to save progress.