I own two different Tachikawa pen holders, but this is the one that I use regularly. Before the Tachikawas I had the standard Speedball penholders, which are fine too except I noticed that my nibs get stuck in Speedball holders more often. Besides the comfy grip, what makes this particular pen holder special is the double rubber rings in the tip. This accommodates both types of nibs, alleviating the need for two types of holders, as well as allowing you to insert and remove nibs with ease.
What is your current “can’t create with out it” art supply?