Grapnel Gun

The Grapnel Gun is one of the main gadgets used by the Bat Family. It served as a mode of transportation that enabled the user to travel across vast distances and reach places that were simply out of reach.

Before Arkham Origins
A prototype was shelved at Wayne Enterprises and was not utilized. The Grappling Gun was a line launching, handgun like device used by Batman, that fired a retractable and detachable cable or wire with a mechanized, magnetic or clawed end, the ending of the line being specifically meant to grab and pull a target.

However, even though there was a prototype at Wayne Enterprises, a model mechanically similar to the prototype was built by Bruce Wayne while he was training under Master Kirigi. Bruce was able to use that model in his combat and ninjitsu training under The Master. That model was not as technologically advanced as the WayneTech prototype, however, as it was built out of supplies that Bruce could find in the temple and dojo, such as spare wood and loose rope.

Arkham Origins Incident
Batman used his Grapnel Gun during the Christmas Eve Incident, and used it to grapple up to high ledges in order to escape, get to his destination, or to explore. The Grapnel Accelerator sped up the grapple and allowed a jump to be made over ledges similar to the Grapnel Boost in Arkham City, but slower.

Deathstroke also used a gadget completely identical to Batman's, although, instead of solid black, it was stylized orange and gray to match his iconic armor. Deathstroke, besides just using it as a high advantage, also used it identically to the Batclaw, and ripped off vent covers, pulled down enemies, etc.

Arkham Asylum Incident
The Grapnel Gun was in Batman's inventory since the beginning of the game. It also helped Batman to get to high places, and was one of the few items that he couldn't upgrade in the game. However, due to the nature of the Batsuit Batman was wearing (a bare bone basic Batsuit for emergency deployments), the Grapnel Gun he had on this particular outfit did not feature the Grapnel Accelerator nor its upgraded counterpart, the Grapnel Boost, as it was in development at this time.

Arkham City Incident
Again, the Grapnel Gun helped Batman to get to high places, and Batman could upgrade it with the Grapnel Boost Prototype. After he completed a set of augmented training challenges, Batman contacted Alfred and requested the boost, but Alfred thought that it would not work claiming it was still in the prototype stages. However, he sent it to Amusement Mile where Batman claimed it and utilized it for the rest of the night with no issues.

Robin and Nightwing also used their Grapnel Guns, though their versions lacked the Grapnel Boost feature.

Arkham VR Incident
In Arkham VR the Grapnel Gun was a mishmash between the traditional Grapnel Gun in previous games and the Batclaw. Like the previous iterations of the gadget, it is mostly used for exploration, but due to the environmental limitations of the VR world, it is used mostly in the Batcave. It can, however, now be selected as a gadget.

Arkham Knight Incident
The Grapnel Gun worked identically like the previous versions, but Batman automatically started with the level one boost. It was later upgraded to level 2 upon donning the Batsuit 8.03, and could be further upgraded twice with WayneTech Upgrades. When fully upgraded, it launched Batman several meters over the ledge and gave a massive speed boost. The previous levels could still be used after obtaining the upgrades. However, like in Arkham City, Batman was the only one capable of using the boost due to his new Batsuit being designed to handle the G Forces that the new Grapnel Boost causes.

It was also now possible to chain multiple grapples by pressing the grapple button again while prompted during a grapple, as was changing the direction of the boost by holding the movement control to the desired direction.

Playable Characters Who Use Grapnel Gun/ Hook

 * Batman
 * Robin
 * Nightwing
 * Batgirl
 * Deathstroke
 * Azrael
 * Red Hood
 * Bruce Wayne

Trivia

 * The Grapnel Gun was also known as the Grapple Hook or the Grapple Gun.
 * In Arkham Origins, the Grapnel Accelerator was not in prototype stage unlike the Grapnel Boost from Arkham City. The Grapnel Accelerator was slightly slower than the Grapnel Boost, so it was likely that the Grapnel Boost was an upgraded version of the Grapnel Accelerator.
 * A lot of Batman's gadgets were based on the Grapnel Gun, such as the REC Gun and the Batclaw.
 * Arkham Asylum is the only game in which Batman doesn't have Grapnel Boost/Accelerator. It is also the only game where Batman can't grapnel while gliding.