This is a variation of th3we's Cube pen holder, http://www.thingiverse.com/thing:229590. I made my own and then designed a round version as well. Some pictures may have slightly different versions as I customized one with my company's logo which I did not upload.

[Update: uploaded updated versions with a rounded edge to the bottom, inside corner of the round pencil holder and I rounded off the top edges of the square pencil holder for a much cleaner look. (picture soon...)