I really appreciate that people in my city place their old books in small boxes with a "zu verschenken" (free to take) sign when they want to give them away. I've found many great books this way, along with a few quirky and unusual ones too.
Weird little drinking related story about finding my glasses from my college times: Got accepted for a PhD and wanted to party. Met a good friend and went to a Balkans party with loads of cheap booze. Wake up at 6am in a night bus out of town and can't find my wallet on me. Run like crazy to the club/bar where the party was. Last people there let me search for my wallet. Only find my glasses in the bar toilet that I didn't notice I had also lost. Lock credit card and go home happy that I at least found my glasses.
Oh, I found such a thing three different times, yesterday! In a county office, an employee patiently, compassionately, happily helping an elderly lady with paperwork; at a takeout restaurant, a genuinely happy individual who graced me with a smile that would shame the sun, in it's glory, an authentic wish for a great day and a hug, at another business, another absolutely fabulous smile from a spry elderly lady with the most brilliant gray hair.
I've got a pair of vice grips somewhere in my flat.
It's not even that big of a flat, and I don't even have that much stuff. There's no way I ever left the flat with them. Yet they've completely disappeared.
I think it would be cool to stumble upon something of archeological value while on a hike. Like some ancient statuette, or something like a cuneiform tablet.
Motivation is fleeting. Discipline is a trained skill.
Whatever thing you wish you had motivation for, make a schedule for yourself and start doing it. Pair it with something you like ("I run each morning and I get my morning coffee after I finish my run") and stick to it.
Legible notes, especially those intended to be personal. I absolutely love buying used books and finding notes in them (either between the pages or written on them). Crumpled notes, shopping lists, discarded notebooks.
If I wasn't poor, I would prefer those to the banality of money.
Found within my own home/possessions, a jolly rancher hard candy.
Out in the wild, a geocache. I go searching for them intentionally on occasion, but I also just spot one while I'm not looking and those are my fave. Especially the really tiny ones, "oh, that bolt on that stop sign looks a little weird. Hey, it's a nano cache!"
I also go hiking a lot and it's always fun finding plants I have high confidence that they are edible. I cooked up quite a bit of wild fern this spring, now it's berries and mushrooms.
The last time I was pleasantly surprised to find something somewhere, I was looking through store shelves and found an old food I used to like, toaster muffins.