I know this is not exactly what the OP asked for but my favorite labour of love project is by a friend of my dad.

He started in 1979 building this:

http://000fff.org/uploads/ur/IMG_1831.JPG

http://000fff.org/uploads/ur/IMG_1832.JPG

http://000fff.org/uploads/ur/IMG_1833.JPG

http://000fff.org/uploads/ur/IMG_1834.JPG

http://000fff.org/uploads/ur/IMG_1835.JPG

http://000fff.org/uploads/ur/IMG_1836.JPG

Everything is handmade as in everything. One of the gears takes 400 years to rotate around it's own axis.

It's half size of this watch https://en.wikipedia.org/wiki/Jens_Olsen%27s_World_Clock

Besides that he managed to build a succesful security company, countless digital watches (big and small) and even a freaking small harbour and countless other things. He speaks assembler almost as well as he speaks his native language Danish which is why I feel ok posting about him in this thread :)

Claims that there are no modern day da Vinci does not apply to him.