Notable appearances: Comics, Batman (1989), Batman: The Animated Series, Batman Begins, The Dark Knight
For a hero who can’t fly, yet has to travel the length of one of the largest cities on Earth in a timely fashion, it was vital for Batman to invent a way to swing from building to building without the danger of falling to his death. Thus, the Caped Crusader thought up the legendary grappling gun. With the ability to support his body weight—and often times that of another person—this gun fires out a cable that can attach to buildings, police helicopters, or any other object in his way allowing him to swing freely.
In all of the recent comics, cartoons, and movies, Batman has had some version of this gadget on his utility belt. Over the years the design has gotten smaller and smaller, while the cable itself has gotten stronger and longer. And when Batman isn't using it for transport, it can also be implemented as an offensive gadget to tie up crooks or rip chunks of wall down upon unsuspecting criminals.