Us; the group including the speaker as the object of a verb or preposition when that group also is the subject.
We; intensifies the subject as the group including the speaker, especially to indicate that no one else satisfies the predicate.
The reflexive case of they, the third-person plural personal pronoun. The group of people, animals, or objects previously mentioned, as the object of a verb or following a preposition (also used for emphasis).
The reflexive case of they, the third-person singular personal pronoun. The single person previously mentioned, as the object of a verb or following a preposition (also used for emphasis).