UnlockablesUnlimited AmmoGet an S rank in all the missions on Hard to be able to upgrade a weapon to level 5 for unlimited ammo.
Unlock Cooperative Mode in ALL MissionsTo unlock Cooperative mode in all missions, including the sub-missions (Wesker's missions), simply complete "The Fourth Survivor" sub-mission on any difficulty. An option will appear on the right when selecting characters that looks like two pistols and says "begin play with 2 players". Both players play as the same character, there are just two aiming reticles on the screen to play with.
Unlock Extra ScenariosBeginnings 1 - Beat Train Derailment 3
Beginnings 2 - Beat Beginnings 1
Dark Legacy 1 - Complete Fall Of Umbrella 3
Dark Legacy 2 - Complete Death's Door and Nightmare 2
Death's Door - Beat Raccoon's Destruction 3 with an A rank
Fourth Survivor - Complete Dark Legacy 2
Nightmare 1 - Complete Mansion Incident 1
Nightmare 2 - Beat Nightmare 1
Rebirth 1 - Beat Mansion Incident 3
Rebirth 2 - Beat Rebirth 1
The 4th Survivor - Beat Dark Legacy 2
Unlock Past ItemsTo unlock the items from past Resident Evil games, you need to earn an "A" or "S" rank on the respectable chapter.
Battery - Complete Dark Legacy 2 with "S" rank
Blue/Green Leech Charm - Complete Train Derailment 3 with "A" rank
Blue/Red/Green Chemical - Complete Umbrella's End 2 with "A" rank
Blue/Red/Yellow Gemstone - Complete Rebirth 2 with "A" rank
Book of Wisdom/Future Compass - Complete Raccoon's Destruction 1 with "S" rank
Briefcase - Complete Train Derailment 1 with "S" rank
Chronos Key - Complete Raccoon's Destruction 3 with "S" rank
Clark/Gail X-Ray - Complete Rebirth 1 with "A" rank
Crystal/Obsidian/Amber Ball - Complete Raccoon's Destruction 3 with "A" rank
Cylinder Shaft - Complete Nightmare 1 with "A" rank
Death Mask - Complete Rebirth 2 with "S" rank
Eagle/Serpent/Jaguar Stone - Complete Fourth Survivor with "S" rank
Emblem/Gold Emblem - Complete Nightmare 2 with "S" rank
Film A/B/C/D - Complete Umbrella's End 1 with "S" rank
Fire/Water Key - Complete Beginning 2 with "A" rank
Fuel Canteen - Complete Mansion Incident 3 with "S" rank
G-Virus - Complete Fourth Survivor with "A" rank
Hex Crank - Complete Nightmare 1 with "S" rank
Ink Ribbon - Complete Umbrella's End 3 with "S" rank
Joint N/S Plug - Complete Raccoon's Destruction 2 with "A" rank
King/Knight/Bishop/Rook Plug - Complete Dark Legacy 1 with "A" rank
Last Book, Vol. 1/2 - Complete Nightmare 2 with "A" rank
Lighter Fluid - Complete Raccoon's Destruction 2 with "S" rank
Medium Base - Complete Dark Legacy 1 with "S" rank
Microfilm A/B - Complete Beginning 2 with "S" rank
Mixing Set - Complete Train Derailment 1 with "A" rank
MO Disk - Complete Mansion Incident 3 with "A" rank
Motherboard - Complete Beginning 1 with "A" rank
Picture (Ada and John) - Complete Death's Door with "A" rank
Plastic Bomb/Detonator - Complete Umbrella's End 1 with "A" rank
Relief of Discipline/Obedience/Unity - Complete Train Derailment 2 with "S" rank
S.T.A.R.S. Card (Brad's) - Complete Death's Door with "S" rank
S.T.A.R.S. Card (Jill's) - Complete Raccoon's Destruction 1 with "A" rank
Slide Cartridge - Complete Rebirth 1 with "S" rank
Spade/Diamond/Club/Heart Key - Complete Dark Legacy 2 with "A" rank
Square Crank - Complete Umbrella's End 2 with "S" rank
Statue of Good/Evil - Complete Train Derailment 2 with "A" rank
Sterilizing Agent - Complete Train Derailment 3 with "S" rank
Sun/Star/Moon Crest - Complete Mansion Incident 2 with "A" rank
V-Jolt - Complete Mansion Incident 2 with "S" rank
Vaccine - Complete Umbrella's End 3 with "A" rank
Valve Handle - Complete Beginning 1 with "S" rank
Unlock Special StageComplete all scenarios and sub-scenarios to unlock the Special Stage minigame.
SecretsUnlocking the HandcannonWhen you unlock HUNK's scenario, Fourth Survivor, and play through it, there is a secret room located in the police station lobby. It is located next to the front doors. When you walk past this room, HUNK will face the doors leading into it for a brief moment; at this time, shoot the doors and they will open, taking you to the secret room. Inside is the handcannon, it is located on a desk at the left of the room.
source: gamefaqs