It may not be an "official" L4D2 Mutation, but "Jockey Riders" is nothing short of hilarious - and awesome.
The premise is simple: In vanilla L4D2, the Jockey jumps on a Survivor's back, steering them into danger and taking them out of the fight unless they're saved by a coworker. The Survivor can try and fight the Jockey's control, making it harder for the Jockey to steer it where it wants, but that's difficult to master.
But what if the Survivor and Jockey worked together?
That's the premise of "Jockey Riders," a fan-created ruleset that you see in the video above. The Jockey and Survivor must work together in L4D2's version of a three-legged race: The first duo to the Safehouse wins! While the Survivors have God Mode on to protect them for damage, they can still be stopped by other zombies and knocked down by Tanks, slowing their progress.
This is a hilarious and creative fan-made set of rules, and I love it. Come on Valve, can we get this officially added to the Mutation rotation? Whaddya say?