Fans of Barry Allen aka The Flash have seen him interact with several other speedsters over the years in the Arrowverse as well as other live-action and animated media. Some of the speedsters have proven to be much stronger than him, though he has always managed to stand out in the end. After all, he is one of DC's golden geese.
The speedsters lucky enough to have been portrayed by actors aren't the only ones that exist. There are a couple of others that still remain comic-exclusive. It's likely that some of them will still get the live-action or animation treatment in the near future. As of the moment, only the pages are their homes.
Black Racer
The Black Racer speeds through the galaxy using two cosmically powered celestial skis. First introduced in New Gods #3, he came into existence after Darkseid anchored special powers to the body of Vietnam War veteran Sgt. Willie Walker. Later on, Black Racer was able to flee from Darkseid and be his own man.
His powers include the ability to phase through solid items. He can also kill beings by simply touching them. Black Racer also happens to be immortal and can shift back to the comatose state of Sgt. Willie Walker.
Johnny Chambers aka Johnny Quick
Photographer Mr. Johnny Chambers becomes the superhero known as Johnny Quick after reciting the mathematical formula ("3X2(9YZ)4A") which had initially been inscribed in a Pharaoh's tomb. The DC Golden Age comics character is a big fan of the Flash and this is mostly what motivates him to become a hero too.
Johnny Chambers has a well-developed story. He marries the hero Liberty Belle and the two have a child named Jesse Chambers. They later divorce before Jesse picks up the Johnny Quick mantle, thus making him the new hero.
Red Death
One of the newest speedsters in DC comics, Red Death is a villain who happens to be a blend between The Flash and Batman. Hailing from the Dark Multiverse, Red Death is formed as a result of Bruce Wayne's action. The billionaire becomes angry after failing to move quickly enough to rescue members of his family hence he kidnaps Barry Allen and forces him to give him his powers.
The process goes horribly wrong, causing the two to be merged. Bruce remains in his body but he constantly has Barry inside him, resisting everything he does. On the brighter side, Bruce is now much faster than he has ever been before.
Max Mercury
Max Mercury is introduced in DC's National Comics #5, penned by Jack Cole and illustrated by Chuck Mazoujian. He is sometimes referred to as the "The Whirlwind of the West" due to the force with which he moves.
During his glory days, he teams up with speedsters such as Johnny Quick and Jay Garrick. He also fights with villains such as Savitar and Dr. Morlo. After a fight with Rival, he remains trapped in the speed force until the Crisis On Infinite Earths event.
Bizarro
Live-action fans aren't exactly unfamiliar with Bizarro. He has interacted with Clark Kent in Smallville. He has also interacted with Stargirl. However, in the comics, there is a version of Bizarro that is a speedster.
Bizarro-Flash comes into existence when Bizarro clones Flash. He holds a mallet at all times because the Flash happened to be holding one when he was cloned. Though he has the same powers as the Flash, he exists in spirit form and cannot be touched.
John Fox
Fox first appears in Flash Special #1, penned by Mark Waid and illustrated by Mike Parobeck. He lives in the 27th century and is a historian for the National Academy of Science in Central City. Fox goes back in time to seek the help of The Flash in defeating the villain Mota.
Though Fox fails in his mission, the tachyon radiation that transported him through time ends up giving him superspeed. Not needing The Flash anymore, he uses his newfound powers to defeat Mota on his own. He later travels to the 853rd century where he joins the "Justice Legion A."
Sela Allen
Sela Allen starts out as a normal woman living in the 23rd century. When Cobalt Blue takes away her electrical impulses, she becomes too slow to the world, the same way the world is to the Flash.
In an effort to bring her back to normalcy, her father brings her into contact with the Speed Force. She then becomes a human manifestation of the Speed Force itself. She is able to lend the power of speed to any person she wishes.
Teri Magnus
Teri Magnus first appears in Justice League 3000 by Keith Giffen. It's the year 3000 and the villainous organization known as the Five has taken control of the universe. The Justice League is dead but Teri does an experiment to revive it.
However, the new Justice League turns out to be as villainous as The Seven. Teri also ends up being killed by her own brother but she is revived because copies of her DNA had been made. Her DNA is mixed with the dead Flash's DNA, causing her to have Super Speed.
Joanie Swift
A college student, Swift gains powers after accidentally typing Johnny Quick's formula (3X2(9YZ 4A) during a test. Upon realizing she has powers, she decides to join Johnny Quick in fighting crime but he is initially against the idea. After seeing how determined she is, he accepts her assistance.
Sadly, Swift's time as a superhero is short-lived. When she loses her powers while saving animals, she reads the equation again but she is unable to regain the powers. It turns out Johnny Quick changed the equation. Though he felt bad about it, he figured it was for her own protection.
Hot Pursuit
Little is known about Hot Pursuit's origin. Before the events of Flashpoint, he travels back in time to warn Barry Allen about impending doom. Hot Pursuit is different as he doesn't use Speed Force to move fast. He relies on the Cosmic Motorcycle.
The motorcycle is frequently charged with plenty of electricity in order to work properly and traverse the universe as well as different time zones. Created by writer Geoff Johns and illustrator Francis Manapul, Hot Pursuit first appears in The Flash #6.