OEM makes a molded plastic star driver bit identifier that can be used to identify T10 through T60 and E16 through E16 internal or external star bit sizes. They ship the plastic identifiers on a key ring and price it around $3 to $4.
My question is: Are you going to carry this tool around in your pocket waiting for a time when you’re confronted with an unknown star bolt so you can whip it out and say you need a T10? Or are you going to run into an unknown fastener, go back to your toolbox, get this tool, identify the fastener, and go back to the toolbox to get the right tool? Chances are either you’re so good that you can tell the size by just looking at it, or you’re just going to go back to your toolbox once and grab a bit or socket set.
If you think I’m off my rocker, or if you can think of an even more useless tool, let us know in comments.