Wondering who, if I had to get three other people to join me in a real version of the Left4Dead experience, I'd bring. To make it much simpler, I'd assume that everyone knew how to use weapons and could run/jump/bash zombies in an equally proficient way (without this, I would probably be a terrible choice myself given that apart from the potato cannons my grandpa occasionally made, I've never to my memory fired a firearm).
I suppose most people wouldn't want to name their team, for fear of offending those excluded.