Here is the (non-exhaustive!) list of the dumbest gadgets used by Batman in the movies or in the comics.
Discover the worst gadgets used by Batman in his many appearances, in cinema or in print. By drawing from the countless number of existing comics around the Dark Knight, it is not difficult to find tools that are completely ridiculous or useless. And here is just a small anthology.
Ice skates

Warner Bros.
Immortalized by Batman & Robin, ice skaters seemingly appear when you slam your feet together. While useful for fighting Mister Freeze, they are of little use against any other villain except maybe Captain Cold or Killer Frost. It is still hard to imagine that it is practical to walk with boots where part of the sole is retractable and fits into the shoe. But it’s important to be able to skate at any time!
The bat roller

DC Comics
In the Batman comics n°117, and more precisely the beginning of the adventure “Manhunt in space” (1940), Batman and Robin pursue a man who has stolen “atomic material” and to do this, use bat-rollers, which the narration tells us is one of “the latest inventions” because they are “foldable”. We also see these really superfluous tools at the end of the story. Didn’t our two “Caped Crusaders” have another vehicle at their disposal?
The bat-scale

Warner Bros.
Featured in the 1966 Batman feature film, the bat-ladder is sent up from the batcopter by Batman so it can perform the action of descending, as with any ladder. What is then the particularity of the bat-scale to deserve its name and to distinguish itself from a classic scale? No idea.
The most likely answer is that Adam West’s version of Batman was a show and a movie to laugh at and live in a cartoon world. Let’s take it for a gag if we don’t regret such a ridiculous idea.
The Villain Foil

DC Comics
In the comics Planetary/Batman: Night on Earth (2003), a “cartoon” version of Batman, visually inspired by the version of Adam West from the Batman series of the 60s, attacks a supervillain… with anti-spray super naughty! In addition to making a reference to the no less ridiculous “bat-spray anti sharks” of the 1966 film Batman, it is undoubtedly the most sexist gadget ever invented!
Le batpon

DC Comics
Do you know the famous bat-grapple, immortalized in all the Dark Knight movies and video games? Well before him there was the same thing, only less! The batpon is a mini-harpoon given by Batman to Robin for his birthday. It has the same utility as a bat-grapple, but just has a tiny little hook to hang on to, and you have to believe that a “batpon” sounded better! Note that Batman himself will use this “precious” gadget against Superman in one of the issues of the “Worlds Finest Heroes” comics.
The bat card

Warner Bros.
You expected it if you saw the movie “Batman & Robin”, obviously the bat-credit card doesn’t make any sense. Which bank would accept Batman’s money? Who would accept a permanent card from a superhero whose real name is unknown? What could be the use of Batman having a bank? Investing in bat protection and the leather trade? One more stupid idea for a completely failed film.
The beat train

DC Comics
Have you ever wondered how Batman manages to transport all his gadgets across the country when he leaves Gotham City? Batman comics n°95 answers you with a simple solution: the bat-train. What’s more than a train? It has a Batman mask on the front, making it perfectly recognizable as the Dark Knight’s train, and it relies on existing railroad tracks so doesn’t go unnoticed at all. On paper, it must have sounded like a good idea.