The Sonic Snare is a tool use to catch Slugs by stunning them with sonic pulses. The snare seems to have a detrimental effect on slugs, weakening them so that they are easier to catch. In "The Slugout", Pronto used one to try to catch some Frostcrawlers but it backfired, ending with a mass transformation of the Slugs that damaged Chillbore Cavern. It was used again by Eli and Burpy to defeat the Hooligang by using the snare to target a bunch of Grenukes, causing the slugs to lose their grip on the cave ceiling and rain down upon Billy and the rest of his gang.
The effects of the snare bear a passing resemblance to the way the Shadow Clan sync with slugs, in that both cause the slug's body to glow, eyes to white out, and cause the slug to make noise.