Cube (Portal 2)
prop_physics - entity models/props/metal_box.mdl - world model portal_weighted_cube - in game command line
There are also reflector cubes which can redirect env_portal_laser's
prop_physics - entity models/props/reflection_cube.mdl - world model portal_reflector_cube - in game command line
Cubes are box shaped objects in the portal series, that can be placed on buttons to activate them or bend lasers.