The Novalith Cannon

I believe it is modeled off a giant rail gun.

http://en.wikipedia.org/wiki/Railgun 

The effects would depend on whatever it fires. You could perhaps load the useless 1/3 of a planets population (such executive middle-men or telephone sanitizers) in the warhead and fire it off to help a world's economy. However, I would beware particularly dirty telephones after doing so.    

I think it fires a missile equipped with an FTL drive from a railgun. Of course if this existed in real life, and was used on Earth, the ecosystem would collapse due to the enormous impact crater, or the planet would just have a massive hole running through it, depending on the impact speed. Either way, we wouldn't be having a very good day.

Pack it full of lawyers (parachute and a briefcase) and let the population tear itself apart. That way I can keep the cities.

In-game descriptions and such describe it as a massive nuclear warhead propelled via a railgun apparatus. Given Extended Range Missiles is a requisite research subject, the warhead itself may have its own propellant supply to accelerate itself towards its target once it drops out of phase space.

The warhead's kinetic energy alone is extremely destructive, but adding a nuclear payload to it just makes it absolutely devastating. Effects are known to reduce the overall habitability of a hit planet.

But then the remaining 2/3 of the population might die from an extremely dangerous virus that exists on unsanitized telephones!