The rook test piece

As far as I know, nobody really knows where this model originally came from, but it's by far my favorite test print.

You can also find it here on Thingiverse: 

https://www.thingiverse.com/thing:99028

I print one for every new filament I get. I always print them with 0.2mm and 15% infill. Takes about 2 hours.