difference - When to use "I" and "me" in an answer

I still have problems to figure out when it's right to use I or me in an answer.

For example, what is the right answer to "Who did this?"

If I did it, should I say I or me? I've heard native speakers using both. Is there a rule?

And what are some examples when to use me, and when I?

Answer

Since a full response would be "I did this" (or "I did it"), "I did" and "I" are both correct responses.

However, it is common in cases like this to simply say "me" (although it would not be correct to say "Me did it").

I'm not sure I've ever actually heard "I" as a response to such a question. I certainly wouldn't respond in that way. I would use one of the following:

I did.

I did it.

Me.

It was me.