Here's a list of some things that you can unlock:
For the play through you get different screen filter (horror, comic, etc) and Claire's and Barry's classic outfits.
For single or severe = Chicago Typewriter
For Normal = crossbow
For survival = Pedro’s drill and No Escape Difficulty
For No Escape = Infinite Ammo
Everything on Normal with an S Rank = finish screen filter and the short sword.
S Rank = survival comic screen filter
S Rank No Escape = more screen filter
Game in less than 3 hours finish = Infinite Rocket Launcher
S rank on all levels without weapons = EX B / W Screen Filter
Good Finish = Claire Sniper Costume
Complete all episodes timeout = Bubble Gun (For Natalia)
Complete all episodes = Katana (For Moira) Invisible Mode
Medal Claire - Episode 4 - Kill Five Animals
These animals are waiting at a certain point. As soon as you approach them, they fly or run away and are gone.
1. Rat. Sitting in front of the tool table and runs toward chest, sobalt you are close. But you may be able to target and kill at the fork already.
2. Rat. Immediately after the double lock gate. She sits in front of the military-box and runs against you as soon as it happens. You can also aim at it before you open the gate where both locks. Simply stand next to the door and see where it sits.
3. Nasty Rat. Once you've killed before the military chest, the second rat, the head goes down AND climbs then up again. Since the rat is back in the same place where has the rat no. 2 wait !!
4. and 5. Two ravens. One sits on the second military box (if it comes out with Clair and the timer starts) the other sits directly on the platform above. So as soon as the timer is there, kill both ravens.
Then let only conclude and save and you're a medal richer.