A simple tool for generating arbitrary gear profiles with built in support for involute gearing, herringbone, and if you want to get cute, optimal http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.56.4984&rep=rep1&type=pdf and arbitrary tooth profiles.
It'd also be great if there were an efficient way of storing complex but highly symmetric geometries. I'm finding that after adding something with ~ 200 teeth every save is taking ~10-15 seconds.