I'm not sure if you'd call this "travelling" but I certainly felt unsafe.
If you check the picture below you'll see a tandem hang glider being towed by a Dragonfly ultralight. The Dragonfly was piloted by Birdman Bill Moyes, the man who invented hang gliding. The tandem was piloted by my son, Neil, who had his mother as a passenger. (Once they gain sufficient altitude the glider drops the tow rope and flies freely.)
The strut at the lower right-hand corner of the image belongs to another Dragonfly in which I was a passenger. I was held by only a lap and sash seat belt while I clung to the frame with one hand and operated the camera with the other. That's pretty scary for somebody who is acrophobic.
I was repeatedly followed by a known terrorist car when working for the UK government in Belfast. "They're just trying to put the frighteners on." was what the Police told me. You know what? They succeeded.
I had a gun stuck in my face in Nigeria, and a knife pulled on me in South Africa.
I was threatened with "A real beating" if I didn't stop talking to the local girls in a club in Helsinki (the threatener turned out to be better at running than fighting when push came to shove).
I was told, by the hotel reception to take a cab to travel about half a mile when staying in Detroit once. "Not at all safe to walk!"
So I have, occasionally, felt less than 100% secure.
I'm still alive.
Yes I have, only to realize that my fear was irrational due to being sheltered by my very own home country. I was in Pakistan and for the most part everyone was very welcoming and friendly. Despite what you see on TV. The average person I me is just like you and me, just trying to get by with everyday life.
And then we get bombed/shot by some ISIS/Confederate flag waving lunatic.