A bouncer is type of Fairy weapon created for tunnel wars. It's a wide-bore low-frequency laser blaster. When activated, it shoots a slow deadly beam that bounces from surfaces until hits living creatures, killing them. It's affects can be overridden if the beam is contained moments after it leaves the gun barrel, such as Domovoi Butler demonstrated with Foaly's prototype Safetynet in the second Artemis Fowl novel.
Role in series
Artemis Fowl and the Arctic Incident
The first (and only) time when a bouncer is seen is in Artemis Fowl and the Arctic Incident, when Opal Koboi gave it to the mesmerized Luc Carrère and stated it to be camera, and that he should take picture with it if someone asked about batteries. Butler later showed up, making the mistake to ask about the batteries, and (equipped with the prototype Safetynet) was able to avoid the beam Luc shot by containing it within the Safetynet, since he and Luc couldn't both fit in it.