Left 4 Dead. On the rooftop of No Mercy, waiting for the helicopter, things are going pretty good, using the defensive weapons at a nice, even interval. A tank zombie shows up, I dispatch it with my machine gun. Literally two seconds later another tank shows up, you have got to be kidding me! My team starts to go down, one after the other. I look around and see another tank. I get up onto a high point and can see at least two additional tanks, four tanks, wtf! I start blowing up propane tanks and setting the lower areas of the roof on fire with gas cans, just gotta keep moving, the chopper is almost here.
By now I've lost count of how many tank zombies are on the roof, my whole team is down and I have literally nothing in the way of weapons, health or pickup items, it's just my pistol. As I run to where the chopper will show up, a tank finally runs me off the roof, the camera pulls out to show the rooftop as the chopper arrives, there are about thirty tanks on the roof. Not sure if the AI director is actually allowed to do this or this was some insane glitch.