Weapon cubemap
Entity description

weapon_cubemap in Counter-Strike: Source
This entity gives the player a set of spheres (models/shadertest/envballs.mdl
), each with different reflective surfaces. It is used for checking cubemaps.
The commands to receive the weapon_cubemap (typed into the console) is either impulse 81
or give weapon_cubemap
.
These commands are considered cheats, meaning that sv_cheats must be set to 1, or developer mode must be enabled, for them to work.
You can switch to this weapon (after having received it) by typing use weapon_cubemap
.

bind "X" "impulse 81"; "use weapon_cubemap"
will bind it to the X key. (You may need to press it twice the first time you use it in a map.)