Yeah, im aware of the new technology actually, kepler last year finding what was it, seven almost earth sized presumably rocky planets around a single red dwarf star, among hundreds of others. But still, gas giants arent at all "rare", it frankly would make more sense if they had similar frequency to show up as rocky worlds. Theyd both have some unique properties. Maybe you could extract metallic hydrogen from gas giants, dunno what youd do with it. Use it as a superconducting fluid?
Ice giants, like uranus or neptune, like 5-10 earth-masses, shouldnt be forgotten either. Those planets contain significant percentages of water, in the form of ice, in the outer fringes of a solar system. Theyd have both a solid surface, liquid core, and extreme atmospheric pressure and surface gravity. Which is neat shit. Id want to explore minerals on worlds like those.