The first time I remember was in Copenhagen when I had trouble about the knife I was carrying (1980).
Then I had that issue with the guns when we came back from Spain (2000).
At Washington, D.C., National Airport we had an issue with a pencil sharpener. Not. Kidding. (ok, it was right after they'd re-opened post-9/11, but still).
There was the jam that was confiscated in Canada because I refused to check it (last May).
I'm sure there were other incidents that are not coming to mind at the moment.
Today, when I came back from London I had a really, really hard time with the question,
"What was the purpose of your travel to London?"
I had to push down a very strong urge to reply,
"To visit the Queen!"
But push it down I did. I also pushed down the giggles.
That said, when I was at the customs area and they asked me if I had food I replied, without hesitation,
"No."
The nice young man asked me to put my bags flat on the belt and when they'd passed through he asked, with a slightly accusatory tone and very confidently,
"What food do you have in the bag, ma'am?"
To which I replied, confidently and perhaps a bit defensively,
"None!"
and then, after a pause,
"Oh, I bought cookies at the airport ... "
He asked if perhaps I had an apple.
"No!"
He asked if he could look through the suitcase.
"Of course!"
(still confident).
And what did he find?
My food stash for the flight, which I forgot about. And hadn't opened. It was purchased in Minnesota.
All I could say was,
"Oh! Oooops!"