Half-Life Easter Egg - G-man Id Card

Open half life in developer mode by going to your Windows Start menu, selecting "Run", and typing
"C:\Sierra\Half-Life\hl.exe -dev -toconsole"
Then load a saved game or start a new one and press the button that is at the left of the numbers in your keyboard and type "sv_cheats 1".
Now type "/noclip" and when you see G-man look what is inside his briefcase.