I had a very expensive old-fashioned once where the bartender chiseled a sphere of ice out of a block. It took about five minutes. The diameter was about 8cm or so.

He created a very spherical sphere. I twizzled it round and round but could not detect any eccentricity. Clearance in the tumbler was even at all orientations.

A carved duck might be more immediately impressive, but the sphere did blow my mind.

It was a very good old-fashioned. I nursed it for 20 minutes - it didn't get watery, as they usually do.