Passwords:
The passcode for the Bridge at the panel is: 561
The passcode for the Bronco Masterkey is: 3033
The passcode for raising the Flood Gate is: 18
The passcode for raising the Full Moon Gate is: 15 

Get prizes & BP:
     At  the  Beginning of the game DONT practice! Wait till after the
Akropilis  Tower.  After the Tower get the M4A1. THEN practice with it
and if you do good enough you get prizes and BP! The prizes are Hunter
Goggles  (prevent  Darkness), Lip Balm (prevent Silence) these must be
attached to do so! Shoulder holster armor and other stuff.

Kill the Giant Beast:
     Before  you  got  to  bed at the Motel Room 6 you should have the
Grenade  Pistol  or  the  M4A1, also have Energy Shot and Healing. The
best  place  to  be when fighting The Giant Beast is the Corner of the
Room  6  and  the  Storage  Unit he can't hit you there. Heal whenever
needed  and  keep shooting have plenty of ammo though. If you kill the
Beast you get a protein capsule (+5 health) and later from Mr. Douglas
you get a full automatic Handgun w/ bullet capacity of 100!

Unlock New Modes:
Bounty Mode & Replay Mode - get by finishing game with any character
Supportless Mode - Finish the game with a good ending
Deadly Mode - Finish game with Supportless Mode
Scavenger Mode - Get 69,001 in any mode
Nightmare Mode - Complete Scavenger Mode 

How Modes Affect Your Ratings:
Finishing in Bounty Mode gives a +1 to your rating, 
finishing in Scavenger mode gives a +2, 
Nightmare gives a +3. 
So if you finish Scavenger with a C rating you really get a A! 

Requirements to Unlock Weapons:

Rating Needed Experience Needed Weapon(s) available in the shop 
S 400,001+ FF8 Gunblade, Ringer's Solution, Eau de Toilette  
A 200,001- 400,001 Hyper Velocity, Hunter goggles, MP Boost 2  
B 75,001 - 200,000 MM1, Airburst Grenades, Recovery  
C 72,001 - 75,000 M249, .44 MaedaSP Rounds, Cola  
D 69,001 - 72,000 .44 Mongoose, Magnum Rounds, Skull Crystal  
E 66,001 - 69,000 AS12, R.Slug Rounds, firefly Rounds  
F 62,001 - 66,000 Aya Special, 9mm Spartan Rounds, Lucky Card  
G 57,001 - 62,001 Javelin, MD Player, Holy Water  
H 51,001 - 57,000 Pike, Lipstick, Tactical Armor  
I 44,001 - 51,000 Hammer, Belt Pouch, MP Boost  
J 16,001 - 44,000 M203, Protein Capsule, 9mm Hydra  
K 14,511 - 16,000 M9 Bayonet, M4A1 M Clip, Flare  
L 14,510 or less Monk Robe, Medicine Wheel, Recovery2