The title says it all, I made a particle editor for my current game project and it works well enough for the moment. It has most of the features that I need like adding / removing emitters and affectors, combining different particle systems and loading in meshes and attaching the system to a tagpoint to get a hint of how it will look ingame. It is written in C# and I have probably spent 20-30 hours on it over the course of a couple of weeks, this includes time spent on creating the particle engine as well.