Averted by Jasmine "Jazz" Fenton of Danny Phantom. She wasn't a spitfire. She was a stuck-up (but caring) know-it-all. But her mother, Maddie, on the other hand...note but she's got brown hair; in fact, most fans think Jazz and her brother are adopted.
Quinn Morgendorffer in Daria, when she gets really worked up. Daria Morgendorffer herself is auburn-haired (red-brown), and when annoyed...bad things happen in her presence. Prime example: in the Season 1 finale, a former student (and perennial Jerk Jock, as well as a Jerkass) disses Daria and her best friend - and moments later, is killed when a goalpost falls on him. Even the passive Fiery Redhead girls can cause damage.
Darkwing Duck's adopted daughter Gosalyn. She is fierce and spirited and has red hair.
Dexter from Dexter's Laboratory. His family is split evenly between this and the Dumb Blonde stereotype; he and his mother are fiery redheads and his sister and dad are happy-go-lucky yellow-haired ditzes.
Rainbow Dash is a tomboy with tons of attitude, and though her mane has enough colours to fit her name, her bangs are warmer colors (red, orange, and yellow) and are more prominent, while the cooler colors (green, blue, and purple) are mostly hidden behind her neck.
Sunset Shimmer is ambitious, testy, sarcastic, hot-tempered, and red-haired — although admittedly her hair's about an even mix of red and yellow.
Pepper Ann Pearson from the ABC cartoon Pepper Ann. Though she's more spacy and neurotic than fiery. In the uniform episode she admits that it's auburn, which other characters agree to once she tries to take credit for being the trope.
Subverted with Gretchen Grundler from Recess, as she's pretty easygoing, unless you make her really mad. She and raven-haired Spinelli actually swap their normal hair tropes: Gretchen's the brainy one (who was going to have black hair originally), while Spinelli's the fiery one. Played straight with Ashley Q.
As flashbacks show us, Miss Finster was a redhead, and still fiery.
The Scotsman from Samurai Jack is a loud, brutish warrior (and about the closest thing Jack has to a friend). Then there's his wife, who's even louder and more bad tempered than he is.
Kyle is this, often instigated as a result of Cartman's antisemitism, racism, or greed. This can lead to his own Jerkass tendencies, approaching Knight Templar at times. His mother, too, is a full blown fiery Jewish Knight Templar redhead.
Also, Darryl Weathers, leader of an angry band of hicks bent on driving away the job-stealing "Goobacks" who immigrated from the future.
The Adventures of Teddy Ruxpin has the young Hot-Blooded Prince Arin, whom the others often have to restrain from going off half-cocked charging into everything. (Though his red hair is usually hidden underneath a helmet.)
Tyrone from The Backyardigans is usually a pretty mellow Deadpan Snarker, but he's been shown to have quite a temper in some episodes, like "Best Clowns in Town" and "Sinbad Sails Alone".
Blitzy Zulander from The Bots Master is easily the more hot-headed of the Zulander siblings, preferring full-on assaults against the Corp. She's also the main pilot of the combining Humongous Mecha Jungle Fiver.
Averted in The Powerpuff Girls by calm, rational, redheaded Blossom. The 'fiery' one though is the brunette-haired Buttercup.
Although she insists that she IS a fiery redhead in one of the interview promos for The Movie.
Headstrong, passionate, and excitable Ray Stantz becomes one in The Real Ghostbusters and its 90s successor Extreme Ghostbusters thanks to an Adaptation Dye-Job (his hair is brown [Dan Aykroyd's natural hair color] in the movies). Ditto the Ghostbusters' Sassy Secretary Janine Melnitz, though to a lesser extent as her hair was already a reddish-brown color in the first movie.
Averted in the comic books, where she is more chatty than bratty when she was first created.
Otto Osworth from Time Squad. While he's generally outgoing and friendly towards everyone around him, he doesn't appreciate it when adults are mean to him or do something incredibly stupid. Sometimes, the attitude towards these types of people are just plain spiteful. He will often argue and lose his temper all together a few times. Sometimes, he will work out a plan that has the sole purpose of simply humiliating someone, let alone get a mission completed.
Same goes with Izzy on the Total Drama series. In Revenge of the Island, the normally level-headed Zoey can get this way when provoked.
However, Gabriella seems to be more spitfire than her daughter mentioned above.
Cliffjumper of Transformers is a hotheaded little red Autobot who is extremely paranoid and eager to blindly charge into a fight.
Ironhide is a crusty old veteran, but is also eager to wade into a good fight. Has a red 'helmet' and main body.
Hot Rod is brash, impetuous, and outspoken as a young Autobot, and retains a primarily red/magenta color. Averted later as he becomes solidly brick red as Rodimus Prime, but also becomes more morose, brooding, and jaded.
Warpath is a shouty Boisterous Bruiser with no subtlety and a love of combat, and turns into a maroon tank.
Speedy, aka Red Arrow, in Young Justice. He was tickedoff at constantly being Green Arrow's sidekick and set off on his own. Despite this, he genuinely cares about his friends and looks after them. In secret.