Pat the Scientist (computer or otherwise)
Pat: So, what are you studying?
Me: Rhetoric.
Pat: How is that useful?
Me: You don't think studying the primary means of human interaction is useful?
Pat: Well, what I meant was how does that get you a job or produce something worthwhile to society like a toaster, or Angry Birds, or cold fusion?
Me: Um, well you see I want to be a professor and I think rhetori...
Pat: Ha, a professor? The humanities are going to be phased out of the university in a few years because they're totally worthless. SCIENCE AND MATH FOREVER BRO! YEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAH.- Sov
So, apparently my name is Pat now.
When I was undergrad, my Biology major never raised any eyebrows. But then, most of my friends were children of immigrants, and most people I met were from the same general community, so everyone understood that "biology" was code for "med school."
Since I've gone on to grad school in biostatistics (med school turned out to be too easy/boring), people tend give answers like "Whoa, you must be really smart." No one ever asks what it is, even though I'm pretty sure no one I speak to ever knows what it is. Or, of course, the classic "Math is way too hard for me; you must be a genius."
My response used to be some sort of self-deprecating humor, if I wanted them to like me. Or, if they emphasized how hard math is, I'd say that anyone could do it with effort, like any other learned skill. If they emphasized that I was born with great abilities (yes, granted, I'm smarter than the average bear, but not actually any sort of brilliant - I was also born with a flat ass, well suited to sitting in the library for many many hours) then I would usually just change the subject.
I always found it kind of insulting that if I did something they didn't, it musn't be because I worked so damn hard for it, but because I was born lucky. They never assume that math was always my weak spot in school, and that I chose a mathy grad program *because* it would be difficult and stimulating and actually provide me with fulfilling challenges.
Nowadays my answer's usually just a simple "Yes." I'm sick of bearing the work of all the conversation awkwardness 'cause of their own damn retarded responses.