Once, when returning to the US, I was asked why I was wearing a coat. Because it's December and I just flew in from Frankfurt, you dunderhead...
Weirder were the two times an agent suggested that with my background I should join an intelligence agency. I was working on dual CS and international relations degrees at the time, which I did not mention to the agent. I should really file a FOIA request on myself to find out what was in my file that prompted those questions.
Agreed. I am getting progressively more upset at the quantity of questions I get--and I'm not the only one; it is trivial to hear what is being asked of others at the same arrivals hall in the citizens-only line--asked when returning to the United States.
I realize this is probably not a controversial opinion around these parts, but since, as a US citizen, I am guaranteed the right of entry into my own country, I believe the questions should be limited solely to establishing my identity. Where I went, why I went, and what I did while I was there are none of my government's business, absent being accused of a crime.
One time I got asked why I claimed to have gone to a place on vacation but my spouse wasn't traveling with me. That seems very out of line to me.