What is the best weapon and why?

I find that I get the most control, kills and headshots with the M-16 and prefer not to use explosives.
But what do you guys use? And does anyone have hints on ways to better utilize certain weapons?

I noticed things have been a bit slow around here. And there's only so much I can do about that. I know most of you just want a relevant icon to put on your userpage, but it would be nice to get a little participation going on in here.

So, I'm going to start posting discussion points on a weekly basis ... they may be funny or serious or thoughtful or stupid, but they will usually be relevant to Left4Dead if not a zombie apocalypse scenario.

This week I want to know, How would you survive the zombie apocalypse (keeping in mind all the special zombies in L4D)?

I can't say as I have one per se, but I definitely think that the characters from the first L4D are more interesting and fun to play.

Who is your favorite and why?

*EDIT* consensus says Francis!