Some people commenting on little rocket man..., I carried the god damn gnome all the way to the rocket. And didn't close the door. And didn't get the achievement. And I had overwritten the save. And I had (still have to do it) to replay halfway through the game (again) to CLOSE THE TRAP.
Nothing special in L4D CAN (!) be done. It's difficult, but I was screaming so much of joy when we finally got it (after about 1 month trying) that I couldn't believe it.
I'm taking out all those "collect x of y" or "follow this youtube to get achievement" things. As in Assassin's creed. I got all the flags in Masyaf (the assassin's HQ) and I promised myself NEVER to do that again. Of course I followed a guide. That's not an achievement. It's a grindfest.
Also, Bioshock Brass Balls is not that difficult. Just play any other FPS on hard (L4D on expert?) and you will more or less get the pace of it. I used the last run to get that achievement (hard, no vitachambers) plus collect all the tapes (it's not like the flag thingy. the tapes have back story), upgrade all the weapons, and it wasn't that horrible (yes, big daddies are still hard. And they kill you in 2 hits).
Finally, +1 in CoD4's veteran achievements. I have gotten until.... After the sniper part 1, when you are in the farm (after rescuing the informant) and you have to get to the basement. I can't get to the basement without having been killed at least..., well, I've never gotten to the basement on veteran.