I knew someone who was TA'ing a class back when they were in grad school. I heard a story about him - to get ahead of this uncertainty he gave the class three options for what to call him:

1) 'Steve' (his first name)

2) 'Mr. Wolfman' (his last name)

3) 'Darth Wolfman' (funny, obvious not meant to be taken seriously, option)

Guess what the class overwhelmingly voted for? :)