Was having a discussion about why 3d printed canoes would sink yesterday.
It occurred to me that the main reason 3d prints are not know for being watertight is simply that we extrude a round bead and place it on top of another round bead.
It's also why transparent filaments don't print all that transparent.

If you had a square nozzle - you would then be laying a flat bead directly ontop of another flat bead. Both increasing the layer adhesion and watertightness and improve the transparency.

It would also give you sharper corners.

Not sure what effect it would have on curved shapes.
But used for the right model it would improve some models immensely.

I suppose they'd be quite hard to make - but I'd definitely be prepared to pay a premium for a set of square holed nozzles.

Seems obvious when you think about it.