* charlatán/charlatana: This translates more to "chatterbox" in the sense of someone who talks a lot, often about unimportant things, and possibly boastfully. It implies a more negative connotation.
* parlanchín/parlanchina: This is a more neutral term for someone who talks a lot. It doesn't necessarily carry the negative connotation of "charlatán/charlatana."
* hablador/habladura: This literally means "talkative" or "talkativeness," and is a more general term.
The best choice will depend on the context. If you're talking about a child who talks incessantly, `parlanchín/parlanchina` might be best. If you're talking about someone who's a boastful and annoying talker, `charlatán/charlatana` is more appropriate.