The Neutrino 500 is an energy weapon, and a light handgun, just as the rest of the Neutrino Guns. It was invented by Foaly, the LEP Technican and Centaur. It was is used and carried by Julius Root during Recon initiations, when he didn't expect combat, such as in the short story LEPrecon included in the special edition of Artemis Fowl:The Time Paradox and is briefly mentioned in The Artemis Fowl Files. Trouble Kelp has one too and attempts to draw it, but before he use it he is knocked back by a laser burst. It is probably was a standard LEP weapon and firearm (until it was upgraded, probably directly to the Neutrino 2000). Like the rest of the Neutrino weapons, it is non-fatal to the target, but very painful.