Discovering old bombs from WWII. A lot of the time they're still active. This happens surprisingly often. My cousin found one while digging up a plot of land in his garden to build a garage. He dug it out and picked it up, then he decided to call the bomb squad. The first thing they told him was "Whatever you do, don't pick it up". So he placed it down gently and waited for them to arrive. When they arrived, they closed down the street and blew it up in a nearby field.
To give you an idea of how not-important this was to him, instead of watching them blow it up, he decided to go to the pub instead and wait until they opened the street again. You'd think this would be front page news, right? Nope, it was on page 10 of the local newspaper. It happens often enough for most Brits to not give a shit.