Do you love Left 4 Dead 2's Scavenge mode, but wish you could play it cooperatively instead of competitively? Or do you really enjoy playing the last map of the Dead Center campaign with your buddies, but pine for a moving objective? Or are you nuts for Team Fortress 2's Payload mode, but feel it could use more zombies? If you answered "yes!" to any of these questions, then Left 4 Dead 2 player-created mod "Badwater Basin" might just be for you.
You play as the L4D2 survivors on the familiar (well, familiar if you've ever played Team Fortress 2, that is!) Badwater Basin map. There are over 30 gas cans strewn around the map and the survivors must gather a set number of cans in each area to progress the payload to the next checkpoint. At certain checkpoints survivors will have to venture into dark buildings to hit several control panels before the payload can progress. Of course it wouldn't be Left 4 Dead 2 without hordes and hordes of zombies out for survivor blood attacking players the entire time they're attempting to do these things! The end of the line results in a classic wait-for-the-rescue-vehicle scenario while survivors try to hold off more hordes and a tank.
I played this mod with a couple of my friends, and we had a blast. We're big fans of scavenge and the moving objective really made it feel like a completely different mode. It's definitely worth a spin if you're into that sort of thing! You can pick it up on creator jsparakov's site.