"What are you, a saint?" or "What are you? A saint?"
Or is there a better way of punctuating this?
"What are you, a saint?" or "What are you? A saint?"
Or is there a better way of punctuating this?
Either one would be correct, but the two different representations could indicate a slight difference in how they are enunciated.
In the first example, there would be the slightest of pauses after the initial clause, before the final phrase. It would be perceived overall as one sentence, one complete thought.
In the second example, it would likely be spoken with a slightly longer pause after the first sentence. There would be a momentary break (less than a second) for the concept What are you? to register, and then the offered (and disdained) possible answer given, A saint? This second sentence is technically a fragment, but it is easily understood to mean [Are you] a saint?
The latter form would be perceived as more dramatic, and probably more critical.
These distinctions would be very subtle, and either is an appropriate way to convey the overall concept.