And for other pronouns, like when Gandalf said: "YOU SHALL NOT PASS!".

I use it often, but in only one instance. If I'm with a friend or group of friends, and we're about ready to leave to go somewhere, I'll just say "Well, Shall we?" as in "Shall we leave?"

Shall we dance? (Song lyrics) from "The King and I"

Shall is one of the modal verbs used in the "Future Tense" with "I and we" in questions such as "Shall we dance"

When referring to something that you are sure will happen to you in the future you use shall,  "I shall miss him terribly" 

I use it both as an alternative to "will" and also for suggestions, e.g. "Shall we go the pub tonight?".

we use "shall " with the future tense for future action first person pronouns I / we.