Gears of War 3: Unlockable Mutators

In Gears of War 3 for the Xbox 360, there are quite a few Mutators you can unlock to use in the Arcade and Horde modes.

Some of these make the game harder, some make it easier, and some are just for pure silliness. Easy mutators each decrease your experience gained by 25%, and Hard mutators each increase your experience gained by 10%. You can only have three mutators active at once.

Here is the list of mutators you can unlock, organized by category.

Easy Mutators

Big Explosions – Earn 100 Hail Mary ribbons (Boomshot kills from 200 feet in versus matches). Effect: The radius of all explosions are increased to frightening proportions.
Comet – Earn the Gold Shock Trooper medal by getting 1,000 First Blood ribbons. Effect: As you Roadie Run, you build up energy that can be used against enemies
Infinite Ammo – Earn 100 Combat Engineer ribbons (worked on 5 defenses in a single wave of Horde). Effect: starter weapons have infinite ammo
Instagib Melee – Get 200 kills with the Wretch in Beast mode. Effect: Explosive melee damage
Super Reload – Earn the Bronze Master-At-Arms medal by getting a Bronze medal (getting 100 kills in versus) with all five starting weapons. Effect: Increased damage and clip size for active reload

Hard Mutators

Enemy Regen – Earn the Silver Aficionado medal by playing 150 chapters in Arcade mode. Effect: Non-Lambent enemies regenerate health
Friendly Fire – Complete the campaign in 4-Player Co-op. Effect: You team can take damage from other teammates
Must Active Reload – Get the Silver Active Reloader medal by getting 2,500 Perfect Active Reloads. Effect: Every reload must be an active reload or your gun will jam
No Ammo Pickups – Unlocked by default. Effect: No extra ammo, you must pick up weapons from killed enemies
Vampire – Get 100 Executioner ribbons (most executions in a versus match). Effect: You only regenerate health by doing damage to enemies

Fun Mutators

Big Head – Earn the Gold Horder medal by completing 1,000 waves in Horde mode. Effect: Large heads for everyone
Flower Blood – Earn the Silver King of COG medal by earning 2,000,000 points total in Arcade mode. Effect: All blood spatter is replaced with flowers
Headless Chicken – Unlocked by default. Effect: Enemies attack each other for several seconds after they lose their heads
Laugh Track – Complete the Standard campaign, Arcade campaign, Beast mode, and Horde mode on Casual or higher difficulty. Effect: For every kill, you will hear some mature humor
Pinata – Earn the Gold Investor medal by earning a total of $500,000 in Beast mode. Effect: Tokens drop from each kill that earn you points for collecting