-Order of Malta. De Jure recognition, no territory or population to speak of. Basically a forgotten joke country left over from a bygone era.
-Trasnistaria. Has population, land, flag, collects taxes. Only recognized by Russia. There's a few Russian backed puppets like this, I won't name them all.
-Taiwan. Already discussed.
-Hong Kong. Mainland Chinese media calls the protestors terrorists. Yet another example of "terrorist" meaning simply "whoever the establishment wants to de-legitimize". If you follow the CCP narrative, the thing they care about isn't Democracy but separatism. "One China" is about not recognizing Taiwan and HK as a matter of ethno-nationalist principal.
-Palestine. Recognized by majority of UN countries. Still not recognized by US, Israel, and associated power block. Why? Because of the stupid belief that recognition will somehow legitimate it.
-ISIS. At their peak they had a sizeable chunk of land, a flag, a capital, civic functions like a court system, an oil industry, handed out passports, were fighting a conventional land war using conventional (not terrorist/guerilla) tactics, had a uniformed army, and the word "state" was right there in the name. But don't you dare call them a state lest someone mistake you for a terrorist sympathizer.
This is why I subscribe to De Facto nationhood instead. A nation is a nation when it satisfies the following properties:
-A plot of land with well defined borders.
-A permanent population on said land.
-A Monopoly on violence over said land.
-An organization capable of credibly making peace, declaring war, and otherwise accepting agreements with other nations.
The last one is tricky as it only specifies the capability not the actualization. For example, if the organization agrees to peace but the individual factions of the army keep fighting then this condition is not satisfied and what you have is a stateless warlord situation. For another example, the ISIS situation clearly had an organization which was capable of agreeing to a surrender or appointing an ambassador, but they never wanted to or were allowed to. The condition is still satisfied even though they never did it.
Taiwan can do anything it wants without repercussions inside Taiwan, thus ‘monopoly on force’.
China using force in Taiwan would just be a declaration of war.