Easter Eggs

Valve Hammer Editor

Go To Coordinates

If you type the point 200 -4096 1154 in the Go To Coordinates dialog, a dialog appears saying:

Day of Defeat: Source

WTF

The voice command voice_wtf makes the user say Whiskey Tango Foxtrot!

Half-Life: Blue Shift

[1] [2] [3]

Half-Life: Opposing Force

Haiku

Open the console and enter haiku to make the game put together a random  haiku for you. All the lines can be found in the file opfor.dll.

A possible haiku

Team Fortress 2

A birthday Easter Egg!