It is I!
Pop quiz: which of the above exchanges is grammatically correct? If I tell you it’s the second one, would you believe me? Me versus I is a highly confusing issue in the English language. (We’ll deal with myself in a minute.) It all has to do with what (or in this case, who) the subject of the verb is. Sometimes it gets even crazier, because we often use sentence fragments in speech, and you have to imagine or fill in the rest of the sentence to determine the subject.
So in the first example, when you reply to the question “who’s there?” you must imagine using a complete sentence to respond. You wouldn’t say “me is here.” You’d say “I am here.” Therefore, the subject of the verb “am” is not me, but I. That’s why the second example is correct, if a bit Shakespearean-sounding.
It gets even more confusing when there are two people involved.
Who’s going with us?
He and I. / Me and him.
Which one of the above responses is correct? If you knew it was the first one, you’re already applying the rule as noted above. Fill in the rest of the sentence: “He and I are going with you.” The trick is that it becomes clearer if you remove one of the people. “He is going with you.” “I am going with you.” Both are correct, as opposed to “him is going with you/me is going with you” which are clearly wrong when you say them aloud.
This is all to do with subject and object pronouns, by the way. For the first person, I is the subject pronoun and me is the object pronoun, which means that you use I when it is the subject of the verb, and me when it is the object (as in he gave the ticket to me).
But what about the tricky word myself? It’s a reflexive pronoun, a different beast altogether from the first two we’ve discussed. You use a reflexive pronoun to talk about your own person: “I see myself in the mirror.” “I did the job myself.
But you wouldn’t say, for example, “John and myself are going with you,” because it doesn’t work if you take out the other person. “Myself is going with you.” No, you’d just say “I am going with you,” right? Only use myself when you’re the only person in the sentence and when you are its object, not its subject. “I talk to myself sometimes.” “I looked around the room, but only saw myself.”
I hope I’ve managed to clear up this complex issue a little bit for you. And in case you think I did this all myself, I should tip my hat to Grammar Girl over at Quick and Dirty Tips, who provided some excellent examples for me to build on. Check her out for more grammar fun and frolic!