I just spent a couple of hours playing through the first part of Left 4 Dead, No Mercy. What a fantastic game! I highly recommend this game to anyone who has ever watched and enjoyed a zombie flick, including Shaun of the Dead.
In fact, any kind of horror movie where suspense is high on the agenda. I love the quiet moments in this, in fact in many ways they are the scariest as you are just tensing up, WAITING for something to happen.
When all hell breaks loose (excuse the pun) it's hard to maintain your composure and you find yourself yelling and flailing away with your gun hammering the "push away" button and the trigger alternately, trying to create a bit of space for yourself and trying to keep an eye on team mates.