Metal Gear Solid 2: Substance Codes, Secrets and Bugs (PC)

Metal Gear Solid 2: Substance is a multi-platform updated version of the original MGS2 released for the PlayStation 2, as well as the Xbox and PC. The game contains the main Sons of Liberty game with some subtle alterations (including a new infrared effects for the thermal goggles and a new set of dog tags), as well as the inclusion of Boss Survival and Casting Theater modes (both which were not included in the original North American release).

The main addition of Substance is the inclusion of nearly 500 stand-alone missions (similar to those from Metal Gear Solid: VR Missions) with 300 missions set in a VR environment (including a set of missions played for a first person view) and 200 "Alternate Missions" (including bomb disposal missions) that take place in areas from the main game. In Missions mode, the player can choose between Solid Snake and Raiden, as well as unlock alternate outfits for both (such as Raiden in the Cyborg Ninja exoskeleton and Snake in his original sneaking suit from Metal Gear Solid).

Codes

Unlock all playable characters in VR Missions
When you begin a new mission file enter UUDDLRLRBA as your name - Unlock all playable characters in VR missions

Unlockables

Get every character and mission in VR missions
Create a new file, and don't enter any name... Your new file should name itself as "?"

Unlockable Characters
MGS Snake - Get 100% for Raiden, Ninja Raiden, Raiden X, Snake, Pliskin and Tuxedo Snake's VR missions.

Ninja Raiden - Get 50% on Raiden's VR missions.

Pliskin - Get 50% on Snake's VR missions.

Raiden X - Get 100% on Raiden and Ninja Raiden's VR missions.

Tuxedo Snake - Get 100% on Snake and Pliskin's VR missions.

Secrets

USP Supressor and Marines in Boxers.
After completing the Tanker once, play it again. The USP Supressor will now be in the Crow's Nest after fighting your first boss fight. Also, when you reach the last hold, all the Marines will be in their boxers, not just one.

Here's a video showing one of the infamous MGS2: Substance bugs: