6. Smallville's Flash
Smallville was known for telling its own story with the Superman and DC lore, so its version of The Flash was Bart Allen. As DC Comics fans will likely know, Bart is actually the Scarlet Speedster's grandson in the source material and takes on the alias of Impulse. The codename comes with him into Smallville as he becomes a member of the show's Justice League, using his powers for good alongside the likes of Black Canary, Martian Manhunter, Aquaman, Cyborg, Green Arrow and, of course, Clark Kent.
We only get to spend three episodes with Bart throughout Smallville's 10-season journey, so viewers never really get the chance to see him grow into his powers that much (or learn new ones). He already knows a thing or two about how to use his speed when we first meet him, and his subsequent journey is much more character-based, as he learns to use those powers to help others. When he shows up next, he has a suit and has become a member of the show's Justice League.
Bart is a developed speedster with a trick or two up his sleeve. He's also faster than Clark, thanks in no small part to his ability to boost his own speed mid-run. However, we also learn that using his powers too much can wear him out pretty quickly - which was showcased when he suffered a nosebleed after Lex Luthor trapped him and refused to allow him to stop running.
We wish we got to see more of Impulse to appreciate him and his powers in more detail, but as he wasn't the main character of the show, his powers never really got the chance to grow or develop outside of the typical speedster abilities.