$ignorez

$ignorez (as in "ignore the Z axis") is a boolean setting available in almost all Source games that enables cheap sorting. It is mostly used for interface materials, which will always be rendered in front of the 3D world, and skybox materials, which will always be behind.

Note:$ignorez can be used on any textures or models, which means that, if the server allows custom files, it can be used to create a wallhack cheat. This has only been fixed, by disabling it entirely, in Day of Defeat: Source, Team Fortress 2, Counter-Strike: Source and Half-Life 2: Deathmatch. Attempting to use it in those games will print the next error message in the console: "Ignoring material flag $ignorez".