Most Helpful Guy
The costume from big mamas house, lol na I would say just a Large T Shirt from the guy and with/without panties.
Most Helpful Girl
Why you ask? Because a nun costume can be hot if you're really attractive but you're still pretty much covered up.
A teacher? There really is no official teachers look they where what they want so unless you're walking around with one of those sticks they use to hit their students, an apple, and maybe glasses. no one's going to know who you are...
Now a school girl it's clear and can be hot with a skimpy uniform on.
But nurse is the best because most patients find their nurse hot and if you're halfed dressed you'll be even hotter.