Birkenstock sandals, maybe because of the German blood in our family. Formerly in secondary school it was really not done to wear them, and I think it's amazing what is happening now. Women on super high heels and muscular men enter the specialised shop in Rotterdam and leave some later on Birkenstock sandals. I think the company has a genious formula and is able, just like Ikea, to design for everyone. Comfort obviously wins.
For M I bought these slippers and embellished them with a ribbon I ordered right here.