Co-Ex is a fantastic single pitch climb on the MF wall. It is considered "the" 5.10 Gunks testpiece... It's rated 10d, but with the correct beta it should feel, oh, about 11a. It's unbelievable to me that the FFA was done in 1967.
A fantastic route with fun moves and a somewhat devious crux. It should be noted that although this climb is mostly well-protected, the opening moves past the first piece of gear are not, but the climbing is relatively easy. Besides that the route eats gear.
Here's a better description. The start is at a left facing corner right of Try Again. Pull the start and head straight up to the fatty ledge 20ft up. Walk right 15ft along the ledge, and then follow the broken left-angling crack up, and through the overhang. Once you get to the broken left-angling crack, there's TONS of chalk. Beta is not that devious.
I seconded this climb, so my comments are based on that perspective.
A fun start to some good face moves lead to a hard crux move. I nearly pumped out trying to make the move over the roof.
UPDATE: The start of this climb is permanently altered. A climber placed a cam behind the flake (about 10 feet up) and fell. The cam held, but, the flake (large chunk) broke off.