Jack-In-A-Box Bomb

The Jack-In-A-Box Bomb is a gadget used by Harley Quinn and Joker's Henchmen. They appeared in Batman: Arkham Origins Multiplayer, and Batman: Arkham Knight.

Batman: Arkham Origins Multiplayer Incident
Explosives disguised as Jack-in-a-Boxes were utilized by Joker's Henchmen.

Batgirl: A Matter of Family Incident
Five Jack-in-a-Boxes were scattered around Seagate Amusement Park, and acted as collectibles. Finding all of them, along with Joker Teeth and Joker Balloons unlocked an award/trophy.

Before Arkham Knight Incident
Harley Quinn used them during her attack on the Blüdhaven police department.

Batman: Arkham Knight Incident
Multiple Jack-in-a-Boxes were scattered around the halls of Panessa Studios. Destroying all 15 was required to complete Riddler's Revenge. Unlike the boxes found in Batgirl: A Matter of Family, those boxes detonated upon activation.

Gameplay
In Arkham Origins Multiplayer mode, they had a slight cool down after placing one. Only one could be activated at a time. There were multiple variants, which varied from adding damage at the cost of range, vice versa, or even simply stunning an enemy. They detonated when an enemy entered their vicinity, damaging, stunning, or even killing their victim. They were however easily detectable, and could be safely destroyed by shooting at them.

In Arkham Knight, they worked similarly to Batman's Explosive Gel, but with an extra twist. When planted, they played music, which caused any nearby enemies to investigate, and lured them to the trap. If one was quick-fired, Harley didn't start the music, which caused them to be silent. Harley had an unlimited supply of them, but only one could be planted at a time.

The gadget's power also depended on how it was planted; If Harley fully activated the trap, they would instantly take out anybody on their detonation range. However, if they were quick-fired, they only knocked enemies down, leaving enemies vulnerable for a ground takedown.

Trivia

 * In Psychosis Mode, any enemies within the detonation range were labeled as Silly Piggies.