Fire Prism
A Fire Prism is an Eldar heavy anti-grav tank that looks exactly the same as a Falcon except for one minor detail: the prism cannon mounted on its top which is capable of wrecking your prized Predator tank in moments. The cannon focuses a beam of intense light within itself and then unleashes it in a blast of glory which can melt lesser tanks to pieces.
The prism can be fired in one of three modes: "dispersed", low AP pie plate MEQ killer; "lance", high-strength anti-vehicle with the Lance rule; and "focused", decent strength small blast used for tricking you into thinking you have a third option when in actual fact you will be using the other two modes almost exclusively. In older editions, it could increase the power of its shot by combining the beams from other prisms into one huge blast of 'fuck you'.
In Dawn of War the Fire Prism was hideously overpowered and beat the crap out of your squads and even other tanks mercilessly. If you had a squad of these they would fire through your forces, sending men, limbs and terrified kittens flying through the air, and DOW2 gives the Prism the ability to switch between anti-tank and anti-infantry settings just in case you really want to rub it in your opponent's face. But then, as we have established, nothing involving Eldar in DoW was particularly fair...