I've been busted by accidentally letting a safety "click" off, before (rather than easing it down).
...But one of the most spectacular things I have ever seen, is the flashing created by a high-polish octagon barrel. As my little brother was stalking a herd of antelope, I watched from about 3/4 of a mile away. As that Browning 1885 moved around in his arms, the barrel (all 28 inches of it) caught the sun, and caused the most ridiculous strobe effect I have ever seen from a hunter. It looked like he was using a signal mirror.
Until I took his rifle, later that day, walked several hundred yards away, and intentionally "signaled" him with it; he didn't understand why he couldn't get close to the antelope.
