I had another zombie dream, though nothing about L4D in this one. Basically, I was being chased by zombies at night when I got to a car dealership. Up front, I saw a yellow vette with the keys in the ignition, so I jumped in and started to drive away. Then an older lady ran outside the dealership building, screaming at me, "What are you doing? Get back here!"
As I pulled onto the freeway, I figured with all the zombies, she should just jump into a car and take off as well. Then I noticed, in the passenger seat, a box of keys. Oops.