How to earn ‘Gnome Alone’ (the honorary achievement for Gnome Chompski)

There was an eHow article (now archived) detailing how to unlock the achievement, but the basic steps are as follows:

In stage 2 of the Dark Carnival, score 750 points on the shooting game before time runs out. Upon winning, you get Gnome Chompski.

Your party then has to carry Gnome Chompski into the escape vehicle at the end of the campaign. You can drop the Gnome as much as you want, and any player can pick the Gnome up, but you must carry him to the end.

Only melee weapons. So, any usage of any rifle or pistol (especially when you get incapacitated), including the grenade launcher will deny you of the achievement, even if you don't do any damage.

Chainsaw is a melee weapon, too, by the way.

Throwing molotov, pipe, bile jar or shoving zombies around (even killing them with a gun only by shoving) will have no negative effect. Also interesting is that usage of machine guns and stationary turrets won't cancel the achievement either, since they don't count as guns, but part of the environment.

HOWEVER, if you fire one bullet, you have to restart the campaign ALL over. Dying and repeating the map will not reset this (have actually tried it).