Any idea?

Yep. Wheat cent. Probably in a fire... and then got corroded, to boot. Worthless, but fun. I dug a melted 191(7?) Mercury dime once that had obviously been in a fire. It was smooshed out like that- larger than normal in exactly that same way- and very granular. The metal had crystallized somehow. I counted it as a silver coin for my find tallies, though, and put it in my "dug keepers" album anyway. Eventually it broke into several pieces.

 

PS- does this stick to a magnet? The whitish color in places make me wonder if it isn't a melted and rusted 1943 steel cent?

I've never dug one of those, though I should have by now. I always figured they rusted so badly in the ground that my detector's discrimination settings made me ignore whatever signals they gave, if any. The only steelie I've heard of anyone digging up was in a story a dig buddy of mine told about how he'd once dug up a whole roll of cents, with the paper wrapper long since disintegrated. (Yes, it happens.) There was a '43 steel inside that roll, still packed tightly against the others even after the paper had rotted away. Because of that, it had only rusted around the outer edges.