There's a great Facebook page called Ghosts of the Eastern Front. The guys go around digging up battlefields, and routinely turn up guns, shells, helmets, and bodies.
The Ghosts of the Eastern Front Battlefield archaeology - Home | Facebook
When I was stationed on Guam in the 80s it was common for dependent wives picking jungle flowers not far off a trail to report finding a skeleton nearby, usually with a rusty Arisaka barrelled action close at hand. It hadn't been all that long since the last holdout had come out of the jungle.
It was also common to get a call from a mover packing up a guy's household goods reporting live munitions of some sort - usually jap hand grenades found in the boonies.
Once a WWII water mine washed up on the beach. It looked just like the one from Gilligan's Island:
EOD came out and packed explosives around it. They moved us back quite a ways, but when their stuff went off the old mine went off, too. The blast shook the ground and made me stagger, but the thing I remember most is that sand rained down for almost a minute.