Resident Evil: The Mercenaries 3D Cheats - 3DS

Unlock Characters
Claire - Clear Mission 1-3.
Rebecca - Clear Mission 2-3.
Krauser - Clear Mission 3-5.
Barry - Clear Mission 4-5 with a B rank.
Wesker - Clear Mission 5-5.

Unlock Character Weapons
Score SS rank using the character on every Missions up to Mission 5-5. Alternatively, you can spend 10 Nintendo 3DS Play Coins to unlock the character's weapons.

Unlock EX Missions
Once you clear mission 5-5 with atleast B rank the credits should roll. After watching the credits the EX Missions should be available.

Unlock Skills
Handgun Technique - Clear Mission 4-1 with a B rank.
Machine Gun Technique - Clear Mission 4-3 with a B rank.
Maximizer - Clear Mission 4-4 with a B rank.
Medic - Clear Mission 1-3 with a B rank.
Revenge - Clear Mission 4-2 with a B rank.

Unlock Costumes
Barry (American) - Get 20 Medals.
Chris (Pilot) - Mission Level 1-3 get an SS-rank, or get 10 Medals.
Claire (Suit) - Get 25 Medals.
HUNK (Reaper) - Get all A-rank on all Mission Level (except Level Ex).
Jill (RE3) - Get an S-rank on Mission Level 3-5.
Krauser (Exoskaleton) - Get S-rank on Mission Level 5-5.
Rebacca (Nurse) - Get all S-rank on all Mission Level (except Level Ex).
Wesker (Uroboros) - Get a B-rank or above for all Mission.

Unlock Character Loadout
Albert Wesker's loadout - Get rank A or higher on all missions up to 5-5 with Wesker.
Barry Barton's loadout - Get rank A or higher on all missions up to 5-5 with Barry.
Chris Redfield's loadout - Get rank A or higher on all missions up to 5-5 with Chris.
Claire Redfield's loadout - Get rank A or higher on all missions up to 5-5 with Claire.
Jack Krauser's loadout - Get rank A or higher on all missions up to 5-5 with Krauser.
Jill Valentine's loadout - Get rank A or higher on all missions up to 5-5 with Jill.
Extra loadout - Unlock all character loadout.
Hunk's loadout - Get rank A or higher on all missions up to 5-5 with Hunk.
Rebecca Chambers's loadout - Get rank A or higher on all missions up to 5-5 with Rebecca.

Unlock Medals
Hero - Get at least a B-rank on 5-5 to unlock the Ex missions. Then, get at least a B-rank on Ex-1, Ex-2, Ex-3, Ex-4, Ex-5, Ex-6, Ex-7, Ex-8, and Ex-9.
Newcomer - Get at least a B-rank on 1-1, 1-2, and 1-3.
Beginner - Get at least a B-rank on 2-1, 2-2, and 2-3.
Captain - Get at least a B-rank on 5-1, 5-2, 5-3, 5-4, and 5-5.
Rookie - Get at least a B-rank on 3-1, 3-2, 3-3, 3-4, and 3-5.
S.T.A.R.S. - Get at least an A-rank on every mission.
Veteran - Get at least a B-rank on 4-1, 4-2, 4-3, 4-4, and 4-5..

Instantly Obtain 300 Green Herbs
Make sure that you have zero green herbs in your inventory. Locate a green herb and pick it up while using it (on the default control scheme, press the Y and A buttons simultaneously). If your timing was correct, the game will have tried to subtract one herb from a total of zero. This will cause the inventory counter to cyclically roll backwards to its maximum amount, resulting in 300 green herbs available for use. Note that this method will not work online.