Avatar Awards - Successfully complete the indicated task to unlock the corresponding Avatar Award:

Bull Shifters Shirt: Win ten games of Versus.
Depeche Mode Shirt: Rescue Gnome Chompski from the Dark Carnival.
Left 4 Dead 2 Shirt: Win ten games of Scavenge.
Med Kit: Successfully complete all five campaigns.
Zombie Hand Shirt: Kill 10,000 Infected.

Quick healing - Use an adrenaline shot, then use your medikit to heal. This takes a much less time, especially when you are dealing with a horde.

Surviving large hordes - Find a corner, and have a melee weapon equipped. Hold RB while aiming at the approaching zombies. Note: You may get hit a few times.

Defeating special Infected - Use the following tactics to kill special Infected:

Boomer: Shoot at the stomach while staying as far back as possible.

Charger: Get close to it. This will prevent it from charging, and then it can only inflict melee damage. This makes it easier to kill it with any weapon (melee or gun).

Hunter: When it is in its pouncing position, use a shotgun to nudge it away, then shoot it in the face. Alternately, use the shove move while it is jumping at you to force it to stumble back, thus preventing it from landing on you.

Jockey: Get into a huddle with your teammates, and wait for the Jockey to appear. When you see it, all teammates can shoot the Jockey at the same time. Huddling together will prevent it from launching at you. Alternately, use the shove move while it is launching at you to force it to stumble back, thus preventing it from landing on you.

Smoker: Use a similar strategy as with the Charger. You must get directly in front of it before killing it. The Smoker uses its tongue to grab survivors from far distances, but it cannot do that when you are very close.

Spitter: Shoot at the head, and be ready to get out of the way when it spits.

Tank: Go to high ground, and shoot at it while dodging it. In Co-op mode, use a grenade launcher for a frontal assault while your teammates fire at its back with shotguns. Alternately, do not try to deal any damage to the Tank, but instead hide somewhere and let the survivor A.I. kill it.

"Eat Your Brains" song in Swamp Fever: Plank Country - In the bar in the abandoned town, find the jukebox, and play it to hear "Eat Your Brains" by Jonathan Coulton.

Portal reference - In The Parish: The Park, when you reach the bar with the jukebox inside, keep skipping through the songs to eventually hear the song "I'm Still Alive" from Portal.

Easy "A Spittle Help From My Friends" achievement - Start a versus match with friends. Play as the Spitter, and have a friend as the Smoker. Have your friend start choking a survivor with the Smoker, then spit on the survivor with the Spitter while the Smoker is choking them to get the "A Spittle Help From My Friends" achievement.

Easy "Back In The Saddle" achievement - Play against a friend. Jump on the back of a bot as the Jockey, and have your friend melee you off. Run away to recover. Then, jump on a survivor's back to get the "Back In The Saddle" achievement.

Easy "Dismemberment Plan" achievement - In Dead Center: The Atrium Finale in Survival mode, kill the bots so they do not steal your kills. Then, grab the grenade launcher and a bile bomb. Once the horde starts, throw the bile bomb, and wait for a large number of them to get around it. Then, fire the grenade launcher at the horde around the bile bomb. You should get the "Dismemberment Plan" achievement as long as their were a large number of zombies standing around the bile bomb.

Easy "Gong Show" achievement - In Dark Carnival: The Barns, find the strength-testing mini-game in the first area. Inject adrenaline, and hit it with a melee weapon to get the "Gong Show" achievement.

Easy "Guardin' Gnome" achievement - In Dark Carnival: The Fairgrounds, find the shooting range. Score over 500 points to make a garden gnome appear. Carry the gnome to the end of the level, and board the chopper with it at the end of Dark Carnival: The Concert to get the "Guardin' Gnome" achievement.

Easy "Level A Charge" and "Scattering Ram" achievements

Easy "Robbed Zombie" achievement - In Dead Center: The Streets, reach the "Save 4 Less" store where you must get the cola. Kill all the CEDA agents along the way, and collect the vials of Boomer vomit they drop (not all CEDA agents will drop Boomer vomit). If you still need more vials of Boomer vomit once you reach the store, just set off the alarm, and hordes will keep coming with random CEDA agents.

Easy "Rode Hard" achievement - Start a versus match with friends. Play as the Jockey, and have a friend as the Spitter. Then, jump onto a survivor as the Jockey, and steer them into the Spitter's acid to get the "Rode Hard" achievement.

Easy "Shock Jock" achievement - In Dead Center: The Atrium Finale in Survival mode, have a human survivor go up to the top of the stairs, shoot out an area of the glass railing, and jump off so they die. Then, grab the defibrillator, and revive them. Restart the level again, and repeat this until you get the "Shock Jock" achievement.

Easy "Stache Whacker" achievement - In Dark Carnival: The Barns, find the Whack-A-Mole mini-game. Get a score of 42 to get the "Stache Whacker" achievement.

Easy "The Quick And The Dead" achievement - In Dead Center: The Atrium Finale in Survival mode, kill any bots so they cannot revive the human survivor. Grab an adrenaline shot. Then, go up to the top of the stairs, shoot out an area of the glass railing, and have a human survivor fall off where the glass railing was so they are hanging onto the edge. Inject the adrenaline shot, and revive them. Have them fall off the edge again, and revive them again. Repeat this until you get "The Quick And The Dead" achievement.

Easy "Violence In Silence" achievement - In The Parish: The Cemetery, when you reach the impound lot area with all the cars, just use a melee weapon to kill the Infected. The computer players will not set off an alarm. All the red cars have car alarms, so try to stay by the white cars. Once you make it past the area with all the cars without setting off an alarm, you will get the "Violence In Silence" achievement once you make it to the safe house.

Easy "Wing And A Prayer" achievement - Note: All three other players must be bots for this trick to work. Before the alarm goes off, clear all explosive items and do not use incendiary ammo. Then, crouch in the corner near the exit to the plane so the Infected cannot get you from behind or either side. Once the alarm is sounded and the horde start attacking, throw a Molotov to block the entrance. After that, the computer players should stand in front of you and take the damage. Just stay in the same place the entire time, and you should get the "Wing And A Prayer" achievement.

Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

Price Chopper (20 points): Survive the Dead Center campaign.
Midnight Rider (20 points): Survive the Dark Carnival campaign.
Ragin' Cajun (20 points): Survive the Swamp Fever campaign.
Weatherman (20 points): Survive the Hard Rain campaign.
Bridge Burner (20 points): Survive the Parish campaign.
Still Something To Prove (35 points): Survive all campaigns on Expert.
The Real Deal (35 points): Survive a campaign on Expert skill with Realism mode enabled.
Confederacy Of Crunches (30 points): Finish a campaign using only melee weapons.
Head Honcho (15 points): Decapitate 200 Infected with a melee weapon.
Club Dead (15 points): Use every melee weapon to kill Common Infected.
Chain Of Command (15 points): Kill 100 Common Infected with the chainsaw.
Tank Burger (30 points): Kill a Tank with melee weapons.
Shock Jock (30 points): Revive 10 dead Survivors with the defibrillator.
The Quick And The Dead (30 points): Revive 10 incapacitated Survivors while under the speed-boosting effects of adrenaline.
Armory Of One (15 points): Deploy an ammo upgrade and have your team use it.
Burning Sensation (15 points): Ignite 50 Common Infected with incendiary ammo.
Dismemberment Plan (20 points): Kill 15 Infected with a single grenade launcher blast.
Septic Tank (15 points): Use a bile bomb on a Tank.
Crass Menagerie (20 points): Kill one of each Uncommon Infected.
Dead In The Water (20 points): Kill 10 swampy Mudmen while they are in the water.
Robbed Zombie (15 points): Collect 10 vials of Boomer vomit from infected CEDA agents you have killed.
Cl0wnd (15 points): Honk the noses of 10 Clowns.
Fried Piper (15 points): Using a Molotov, burn a Clown leading at least 10 Common Infected.
Level A Charge (15 points): Kill a Charger with a melee weapon while they are charging.
Acid Reflex (15 points): Kill a Spitter before she is able to spit.
A Ride Denied (15 points): Kill a Jockey within 2 seconds of it jumping on a Survivor.
Stache Whacker (15 points): Prove you are faster than Moustachio.
Gong Show (15 points): Prove you are stronger than Moustachio.
Guardin' Gnome (30 points): Rescue Gnome Chompski from the Carnival.
Wing And A Prayer (30 points): Defend yourself at the crashed airliner without taking damage.
Sob Story (30 points): Navigate the sugar mill and reach the safe room without killing any Witches.
Violence In Silence (30 points): Navigate the impound lot and reach the cemetary safe room without tripping any alarms.
Bridge Over Trebled Slaughter (30 points): Cross the bridge finale in less than three minutes.
Heartwarmer (20 points): In a Versus round, leave the saferoom to defibrillate a dead teammate.
Strength In Numbers (15 points): Form a team and beat an enemy team in 4v4 Versus or Scavenge.
Qualified Ride (15 points): As the Jockey, ride a Survivor for more than 12 seconds.
Back In The Saddle (15 points): As the Jockey, ride the Survivors twice in a single life.
Rode Hard, Put Away Wet (20 points): As the Jockey, ride a Survivor and steer them into a Spitter's acid patch.
Great Expectorations (15 points): As the Spitter, hit every Survivor with a single acid patch.
A Spittle Help From My Friends (15 points): As the Spitter, spit on a Survivor being choked by a Smoker.
Scattering Ram (20 points): As the Charger, bowl through the entire enemy team in a single charge.
Meat Tenderizer (20 points): As the Charger, grab a Survivor and smash them into the ground for a solid 15 seconds.
Long Distance Carrier (15 points): As the Charger, grab a Survivor and carry them over 80 feet.
Beat The Rush (15 points): In a Survival round, get a medal only using melee weapons.
Hunting Party (15 points): Win a game of Scavenge.
Gas Guzzler (20 points): Collect 100 gas cans in Scavenge.
Cache And Carry (20 points): Collect 15 gas cans in a single Scavenge round.
Scavenge Hunt (15 points): Stop the enemy team from collecting any gas cans during a Scavenge round.
Fuel Crisis (15 points): Make a Survivor drop a gas can during overtime.
Gas Shortage (20 points): Cause 25 gas can drops as a Special Infected.