"It's I" OR "It's me"?

1) "It's I" (=I am the one)
2) "It's me" (=Me am the one)
Which one sounds correct to you?

Of course when talking informally we can just use any one we like. Nobody cares anyway, right? Even some native speakers use the wrong one too!

BUT, here I'm discussing the standard one which we use in formal writing, formal speech, at schools, during interviews or even in our daily conversation if we want to speak better English.

So, the 'better answer' is "It's I". ;)

MORE EXAMPLES:
1)
Hello. You want to speak to Hafidz? This is him. 
Hello. You want to speak to Hafidz? This is he. - CORRECT
2)
We're going to dinner alone - just you and me.
We're going to dinner alone - just you and I. - CORRECT

3)
It was him who ate all the biscuits.
It was he who ate all the biscuits. - CORRECT

4)
Mom gave both of us, Ziana and I, money for the film.
Mom gave both of us, Ziana and me, money for the film. - CORRECT
('me' is used here because it's an object in the sentence, not a subject )

5) 
The teacher told I to keep quiet.
The teacher told me to keep quiet. - CORRECT *as an object

6)
She is a friend of Hazzi and me.
She is a friend of Hazzi and I.
She is a friend of Hazzi and mine. - CORRECT *to show possession