Check this guide, which provide you all the valid and active codes for the Murder Mystery X Sandbox.
Murder Mystery X Sandbox Codes – Full List
Here is the list with all valid or working codes in MMX Sandbox
Valid Codes
ALLKNIFES: An amazing code, because when you redeem it you receive nearly 100 knives, all the knives (*) available in the game.
NEWPET: Get a Ice Dragon of the Sea Pet after redeeming the code.
RUNI: Not sure what this code gives, but it works.
3MEVENT: Not sure what this code gives, but it works.
Gingerblade, Immortal, Omega Sword, Ultraviolet, Black Reaper, Demon
Heart, Divine, Divine Flame, Gold Reaper, Hallow Blade, HandSaw, Lucky
knive, Orinthian Axe, Permafrost, Shark Sword, Blue Venom, Bolt,
Eastaze, Heartbreaker, Rainbow Runi, Sacred Relic, Sword of Fire, Azure
Slayer, Blaze, Blossom Axe, Crimsom, Earth Blade, Ex0, Frostbite,
harbringer, JD, Purple Haze, Saber, Sea knive, Fish, Chameleon, Caution,
Galaxia, Ginger, Giraffe, Graffiti, Leopard, Polaris, Polka, Venomous,
Cane knive, Ombre, Nebula, One, Pixel, Amber, Amethyst, Blueprint,
Bubbles, Donut, Diamond, Emerald, Frost, Elf, Dragonbreath, Delusion,
Triad, Tropical, Zebra, Tiger, Chalk, Bricks, Blue, Tiled, Turquoise,
Watermelon, Green, Sugar, Taffy, Starry, Slime, Cyan, and as we told you
more than 100 knives, swords and weapons, one of the best codes ever!
How to Redeem Murder Mystery X Sandbox Codes
Go
to the shop (left side of the screen) and enter the code in the shop
window (upper right corner), then click enter and check your rewards in
your inventory. . You can learn how to redeem codes by watching this
video: