When BTC was around 100-200$, I remember someone sharing private keys at a certain time, and if you were quick enough you could transfer fractions of coins to your own key's address. I think that event was actually announced on Bitcointalk..
Out of fun I got over 0.1BTC of it. Some nice few thousand bucks today..
At that time, chain analysis tools to search for "tainted" coins from dark markets were still free to use. ...And of course, it turned out the coins given away were all "tainted"

Indeed, way back in time, I posted a private key in the form of a QR code in the WO thread to celebrate something. Not sure how much was in it. Mine was not tainted, of course.
Generous of you :-)
Every bit back than is now worth some rather serious change...
When I got that 0.1+ BTC, there were about 20 or more private keys posted. (Could have been 50 ... don't remember anymore)
Each address containing about 0.05BTC or so.
Mind blowing that 10$ from that time got valued @ 6-7k$ just some years later ...and certainly more in the coming years..