Gnome Chompski

Gnome Chompski is a garden gnome and improvised weapon exclusive to the Dark Carnival campaign. He made his debut in Valve's Half-Life 2: Episode Two as the Garden Gnome and is infamous for earning you the achievement "Little Rocket Man".

In Left 4 Dead 2, he can be picked up by scoring over 750 points in the shooting gallery minigame at The Fairgrounds and must be taken all the way to the Rescue vehicle in The Concert to unlock the "Guardin' Gnome" Achievement. All players within the entire Dark Carnival campaign play-through will attain the achievement, dead or alive, so long as one Survivor makes it into the rescue chopper with Gnome Chompski in hand.

Gnome Chompski also makes a non-canon appearance in the Suicide Blitz 2 campaign. By bringing him from the first chapter all the way to the end, he can be used to unlock a special Easter Egg.

Tactics

 * Players cannot shoot while holding Gnome Chompski but can still Melee. However, the fatigue timer will still act regularly whenever you push away too many times and the melee is very weak, requiring multiple hits to bring down Infected.
 * When held, the Gnome takes up around 35% of the screen, blocking the holder's right side in near-entirety. You can (probably) circumvent this via the "thirdpersonshoulder" console command.
 * Gnome Chompski is affected by weapon knock-back. If it is dropped under a ramp or on top of a roof and cannot be reached (for example, on the merry-go-round), Survivors may shoot it at an angle to push it back. A Grenade Launcher is effective for this.
 * Gnome Chompski is not a lethal weapon when thrown. Players should not throw the Gnome with the intent to kill with it; it will pass straight through Infected.
 * A useful tactic when carrying Gnome Chompski is to throw it during hectic moments, allowing use of your guns, and then pick him up after. Just be especially careful not to lose it in the fight, or toss him somewhere unreachable. To help keep track of Chompski, you can drop him at your feet with the "use" key (default E) instead of throwing him if needed.
 * There are two spots where having Gnome Chompski could be your downfall: the Crescendo event at the roller coaster, and the Crescendo event at the barns. To make things easier, throw Gnome Chompski over the fence of the coaster so you can cover half the coaster without it blocking your view, and if you should drop it, it is a shorter trip to getting it than if it were back at the entrance. In the barns, as soon as you see the stadium, simply throw it over the railing so it is lying just outside the safe room door.
 * Survivors can pass Gnome Chompski back and forth between each other and take turns shooting. The free-handed teammates can then guard the carrier.
 * In Versus, Special Infected can hit Gnome Chompski out of his box without playing the shooting gallery game. Survivors can then pick it up and carry it to the end of the level, but will not get the achievement because it is impossible to keep it until the finale.
 * Similarily, on any online campaign (Campaign, Realism) if the player has poor connection, they may be able to walk straight up to the closed box containing Gnome Chompski and grab it without playing the game.
 * In very rare cases if you hit the heart-shaped hole on the box with an Axe, Gnome Chompski will have a clipping glitch and may fall through the bottom of the box to be easily obtained.
 * Gnome Chompski can be used to kill Infected, but is ill advised; it takes roughly 4 hits to kill Common Infected on the easiest setting and fatigues the Survivor. More advisable is to throw it and pick it up when the coast is clear.
 * If you are holding Gnome Chompski and a Tank is about to throw a rock at you, it is possible to throw the gnome at the rock to break it. This method, however, is not advised and should only be used at desperate times.
 * Make sure you actually hold Gnome Chompski while entering the helicopter at the finale. Just dropping it will end up with no achievement, therefore you need to start all over again.
 * If the Survivor holding the Gnome presses the elevator button on part one of Dead Center with "Last Gnome on Earth" mutation, the Gnome will disappear through the elevator and out of sight, effectively making the level unbeatable. If this happens, you must restart the level.
 * If the Gnome falls to an unreachable area, such as off a ledge on Dead Center (during the "Last Gnome on Earth" mutation), the level will be unbeatable. If this happens, you must restart the level.
 * Once you have gotten Gnome Chompski to a safe room, if you restart from that safe room it will be with you. So if you lose it somehow while progressing between chapters, you may be better off letting everyone die and respawn at the last safe room than restarting the whole campaign.

Behind the Scenes
Gnome Chompski is a play on Noam Chomsky, a famous linguist, cognitive scientist, and MIT professor.