Bat-grappling gun

The Bat-grappling gun is a fictional item featured in the Batman multimedia franchise. It is considered a major asset in Batman's crime-fighting arsenal, but really only came into prominence with the 1992 cartoon program, Batman: The Animated Series. Since then, it has come to be regarded a common tool of the character. The gun fires a grappling hook attached to a long, tense cord, or batline, that enables Batman to swing from rooftop to rooftop.

Batman: The Animated Series
While James Gordon was arrested under the false charges of accepting bribes from Rupert Thorne, Batman climbed to the top of a building across the street from the Gotham City Jail and used the grappling gun to fire a communication device through the bars of Gordon's window so that he could talk to him.