Particles tester, basically allows you to fiddle with values and when happy save out a Lua snippet that can then be incorporated into your scripts.
Select value to change using I & K keys, adjust values using - & + keys (press Shift key to increment x10)
Attach script to an always active entity, edit script to add your own particle image files and shaders.
Changes in this version:
Added gravity, wind, limb index
Auto-saves values (just in case you select a noin-existant limb index and GG crashes) and reloads on restart.
Multiple output files can be generated
Hold Q for 100x increments
Been there, done that, got all the T-Shirts!