Haywire grenade
From Warhammer 40k - Lexicanum
Haywire Grenades are used by both the Eldar and Dark Eldar for disabling enemy vehicles. Each one sends out a pulse of electromagnetic energy which shorts out electrical wires and disrupts many energy systems. They don't have any effect on biological creatures.1
In 1st Edition, haywire grenades emitted a massive pulse of electro-magnetic energy primarily designed to destroy electronic systems, but could also affect the neural systems of nearby organisms.2-p92