Named Game of the Year by over 50 publications, Valve's début title blends action and adventure with award-winning technology to create a frighteningly realistic world where players must think to survive. Also includes an exciting multiplayer mode that allows you to play against friends and enemies around the world.
Sig 551 from SOF II Gold edition Comes with player and world models.
Wow thats so cool, this is for which gun, MP5?
Yes
how do i download a Half-Life addon?
By downloading it.