A gdi superweapon developed in cnc 1. It reportedly blasted kane's temple of nod in the first war. In the 2nd war, its power increased a bit but wasn't important story wise. In the 3rd war, one blast can wipe out almost anything. and it looks pretty to see when it begins to vaporize and enemy position.
In Tiberian Sun, an ion cannon can destroy an obelisk of light in one shot. In Tiberium Wars, it can destroy the obelisk of light AND anything in a significant radius.