This bowl has Pi written around it in a spiral, and can be printed very quickly in Vase Mode!
It won't come out watertight (or at least mine didn't) but it does look quite cool and would be great for pens or other stationary, especially if you scale it to be thinner.
I designed it in Fusion 360 using the sheet metal tools to unfold a cylinder.
I was inspired by the Tower of Pi (https://www.thingiverse.com/thing:271769) but I didn't want to spend 15 hours or so printing this so I designed this quicker version.
Be sure to enable vase mode for your slicer (I used Cura).