Rainbow Six 3 is a tactical shooter game DEVELOPED by UBI. The game is a first person shooter based on Tom Clancy's best selling novel by the same name. The game has two expansion packs, Athena Sword and Iron Wrath. The plot of Ravenshield is fully explained by Wikipedia (Tom Clancy's Rainbow Six 3). Basically it is all about an elite anti-terrorist group called Rainbow Six, a team bent on foiling the Neo-Facist terrorists doing damages on South American oil interests and European financial institutions.
Twi's Snake Camera for multiplayer servers. Fits through the crack under doors to give you tactical awareness in tough situations, and NOW can even be used to look around corners. Requires the Improved Custom Guns Mod for multiplayer (available here on ModDB).