Cubes

Cubes are common gameplay implements in both Portal and Portal 2.

Weighted Storage Cube
The Weighted Storage Cube was introduced in Portal and remains prevalent in Portal 2. In Portal 2, the blue ring turns yellow when placed upon a Heavy Duty Super-Colliding Super Button.

Weighted Companion Cube
The Weighted Storage Cube was introduced in Portal and remains prevalent in Portal 2. Something here about how Valve wanted players to feel attached to the cube, and realise that they had to keep the same cube throughout that entire chapter in Portal.

Edgeless Safety Cube
The Edgeless Safety Cube was introduced in Portal 2 and is used only in co-op gameplay. It only appears once in singleplayer as garbage. The "cube" is really a sphere; however, it still retains the coloring scheme and patterns present in the designs of the other cubes.

Discouragement Redirection Cube
The Discouragement Redirection Cube was introduced in Portal 2. Its main purpose is to redirect the Thermal Discouragement Beam (a deadly laser) to other directions and through portals.