Being a backyard welder, I'm keen on bagging ferrous materials by the road. I'll hide them further in the puckerbrush and catalogue them in [what's left of] my head for future pickup when I'm in the neighborhood. My permanent truck bike rack is tricked out of some nice fortuitous finds.
Otherwise: tools, the occasional tenner, lots of underwear [wtf?], the odd 'latex expandable'. . .never anything really stunning. Mind you, I wouldn't mind finding the remnants of my mis-spent youth; if you see it let me know. It will look like a Rebel Without a Clue. . .with bushels of long black hair.