Hi, congrats to all the participants. The reveal is really entertaining.
My story: Based on recent improvement with Magic Lantern I purchased an EOS M to do some experiment a month ago, then the EOSHD challenge appeared (but with the Magic Lantern restriction 🙃).
The EOS M was $150, still $50 left for the lens.
The easy choice was a Canon FD, Minolta Rokkor, or the mighty soviet Helios or any vintage lens under $50. But I wanted to try something "different" to stay on the challenge track. A round trip to my treasure chest (my wife has a different name for that box) and I found something quite interesting, an enlarger lens : Beseler-HD 50mm 2.8 - I remember paying something around $30 max. but after checking the invoice and I actually payed $9 + $8 shipping - Then ordered an adapter in Russia - M42x1 to Canon EOS-M for $25.
After 2 weeks, I received a snail mail with some nice Russian stamps and the adapter inside the letter. Added a 17-31 helicoid for focusing infinity and voila an unusual bokeh. Cheers.