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.
Here's a cool player model that me and Waqwarrior did just recently (infact, today!) Extract to your HL or OP4 player models directory. It should be something like this C:\Steam\steamapps\*\ half-life\valve\models\player\