Usage Wars: the singular "they", the singular "themselves", the generic "he"

[SepiaAndDust]

Can they be used to refer to a single person? What if it's referring to a generic person or a person of unknown gender?

Outside of walking into Mordor, in what cases might you use one, instead? Do you prefer it to the singular they?

Or is he the generic pronoun in all (or most) cases?

Is the reflexive themselves ever used to refer to one person? Or would you use the singular themself, which doesn't appear in most dictionaries? Or would you go with the generic himself?

My opinions are that the singular they is perfectly acceptable in all (or almost all) cases, I rarely use one for anything, either reflexive is fine, and the generic he has always been ridiculous.