I have a set of old Eldar guardian plastics. These are the ones that came in 3 parts - the main body, lasgun with right forearm /hand and left hand molded as one piece and the base. The reason the hands/weapon came separate was so that the figures could be repackaged with the hands holding a shuriken catapult cast in metal which can be seen in
this earlier post.
Anyway, what do you do with a bunch of lasgun holding guardians that you can't use? Convert them into Storm Guardians instead. Scrounging my bits box I have many Eldar arm and weapons frames. The conversion itself is a simple matter of removing the lasguns and arms altogether and swapping in new plastic arms with the appropriate weapons. Gotta love plastic minis.
Side by side of original mini with lasgun
and converted Storm Guardian.

For this particular figure I did even less surgery. I left the arms in thier original position and just removed the lasgun part. After cutting the lasgun away from the right hand, I added a shuriken pistol from the weapons frame and re-attached the right forearm at a slightly different angle. For the left side, I cut a fist from one of the arms from the Eldar arm frame and attached a sword from the weapons frame, cut the little nub off the arm and glued the fist in place. By adding different arm and weapons combinations and a head swap or two you end up with a diverse group.
GB