Far Cry 3 coop has an amusing inversion where you have to guard a pickup truck full of "malaria medicine" as it passes through a series of pirate outposts. At first it drives kinda slowly, and the outposts are so close together that it's possible to stick with it (Naturally the driver stops and waits patiently as soon as enemies open fire on him). But towards the end the driver is literally driving off into the nuclear sunset while begging you not to leave him.
It's less frustrating than it sounds. The enemies basically only take potshots at the truck, it has a huge health pool, and you can repair it so rapidly that sometimes its possible to finish before he floors the gas. Or take the easy route and repair it while some pirates are still around so it doesn't leave. The pirates almost always fire on the players instead of the truck, which is merciful.
Another thing which should be a peeve but just makes me laugh: The coop netcode apparently doesn't support vehicle usage at all. You can't ride in the pickup truck or ever get in a vehicle in coop. What makes it funny is: AI drivers are pretty easy to kill. This usually causes the car to slowly come to a stop in the road, wait a couple seconds, then inexplicably explode. The passengers were apparently not briefed on this failsafe, they wait patiently or take potshots until it happens.