Not me but someone who did it in our yard back when I was a wee lad: a gun. Don’t worry. Someone did not drop their gun willy nilly in our lawn, at least not recently. The thing was a very rusty 80-year old revolver. He also found a decent amount of tax tokens.
Digging in my current yard has not resulted in anything as fun: 150 beer bottles, an animal skull (still not sure what species), and a wine bunch of oyster shells.