If vaporising the whole planets ecosystem and all lifeforms on it counts as destruction then the Goa'uld alone have enough weapons to fill a website.
Yeah the asteroid is a good example, although whether it could be counted as a weapon... I mean if you dragged a asteroid into the path of a planet and destroyed both would that be counted as a weapon?
I believe the Goa'uld are capable of wiping entire planets off the map, but why would they bother, its a waste of energy and you could do much better to simply break the military backbone of the inhabitants and enslave the remainder. That also mean you have another military base that you control.
What about Tollan? That planet was destroyed by the race, Tollan. They gave an infinite power source to a race in their own system who then blew up themselves and altered the planet Tollan's path enough for it to be destroyed in a few generations.