Can you end a sentence with am I?

Yes.

You can end a sentence with "am I" as is shown here:

"I'm not that mean, am I?".

I'd think that it'd normally be in the form of a question with some sort of punctuation (like the comma in the example) separating it from the main body of the sentence.

Just make sure that you don't do something like this:

"I'm not that mean. Am I?".

In that sentence "Am I" is a sentence fragment.