I was idly thinking what states of matter are common, which are rare overall. The commonest states of matter in the universe, by total mass, would be gases, solids (mostly as dust), and plasma (mostly as stars). Quite rarer would be the states of matter of white dwarfs, neutron stars, and black holes (if you can call it matter). Liquids, if I am not mistaken, would be the rarest, occurring only on certain planets, and only within a narrow range of interior depths and atmospheric heights. One might argue for further dividing liquids into more exotic high-pressure states (e.g. metallic liquid hydrogen, as in Jupiter), beside the familiar low-pressure ones. This would make the latter, such as water, even rarer from a cosmological point of view.
Do I have this right? Have I missed any rarer states of matter?
Ed.: I have seen Fukugita and Peebles's paper. Since planets overall form the smallest fraction of baryonic matter in the universe, the issue clearly becomes finding the rarest state of matter within planets.