Though not the sort of achievement that makes me proud to be human, the Focke-Achgelis Fa 223 “Drache” (Dragon) was the first helicopter to enter production, though Nazi Germany was only able to manufacture about 20 during World War II. I had no idea it even existed until Aleksander Stein built one from LEGO.
Here’s Aleksander’s Fa 223 in action over southern Bavaria: