L4D Achievments

So they give out a few achievements for the most basic game maneuvers in l4d, which is cool, and then they have super-advanced ones, too.

I'm *all over* brain salad:

http://steamcommunity.com/profiles/76561197993331175/stats/L4D

"BRAIN SALAD: Make 100 headshot kills."

They should list a quanitity on each achievment, because I think I could get 100 brain salads.

There are 2 reasons:
1. I'm scared of running out of ammo. Headshots save bullets
2. I love the M16, pistols. They are both very accurate at long range, especially plus kneeling

I wonder what "catch a rare strain of infection, then pass it to someone else" means. Can survivors get zombified later?

I'm getting used to the idea that anticipation of upcoming threats is pivotal in weapons selection. If you're facing the Horde and you can back into a single room (your back is safe), shotguns are the way to go. It gives scattered shot with stopping power at close range. Perfect.

For open spaces with sniping ability, the M16 is awesome. When you slow, stop, or kneel, the accuracy gets real tight for sniping, plus it's automatic and has a little more stopping power than the Uzi.

...but I see no use for sniper rifles in anything but single player, and single player is boring.  The weapon may as well not exist.