I've been a fan of the tomboy archetype for pretty much as long as I can remember. There are any number of things that can mark a girl as a "tomboy", such as how she dresses, her interests, her general personality, etc. All those things can be pretty cool. (Which is not to say I have anything against more "girly" sorts of girls. They can be pretty cool, too.) Tomboys may disdain "girly" things, or they may embrace them just as much as they do "boyish" things. And not every girl who likes "boyish" things is necessarily a tomboy. (Certainly I try not to call someone a tomboy just because she's a badass, or athletic, or hangs out with boys more than girls, or anything like that.) In fact, some of the girls or women I include on this list may not qualify as such, but I do my best to judge who fits and who doesn't. Some of the ones I include here I got from Council of Geeks' video on the subject, some from Wikipedia's list, and some I came up with myself. But there are some on either list that I didn't include here, either because I don't remember them well enough to make my own judgement, or because I haven't seen/read the things they're from. And... I'm not sure what else to say, except I definitely recommend watching the Council of Geeks video for a more in depth analysis of the topic.

Ace (Doctor Who)
Alex Mack (The Secret World of Alex Mack)
Annabel Andrews (Freaky Friday)
Arya Stark (Game of Thrones)
Ashley Spinelli (Recess)
Audrey Rocio Ramirez (Atlantis: The Lost Empire)
Buttercup (The Powerpuff Girls)
Casey Brown (Candleshoe)
Darlene Conner (Roseanne)
Ellie (Up)
Francie Lawrence (Gidget)
GoGo Tomago (Big Hero 6)
Gosalyn Mallard (Darkwing Duck)
Giulia Marcovaldo (Luca)
Haruka Tenoh (Sailor Moon)
Heather Hobbie (Holly Hobbie)
Jean Louise "Scout" Finch (To Kill a Mockingbird)
Jo March (Little Women)
Jo Polniaczek (The Facts of Life)
Joey Potter (Dawson's Creek)
Kit Keller (A League of Their Own)
Laura Ingalls (Little House on the Prairie)
Lor McQuarrie (The Weekenders)
Lyra Belacqua (His Dark Materials)
Max Mayfield (Stranger Things)
Merida (Brave)
Natty Gann (The Journey of Natty Gann)
Peppermint Patty (Peanuts)
Rainbow Dash (My Little Pony: Friendship Is Magic)
Piper Pinwheeler (Robots)
Red (Fraggle Rock)
Roberta Martin (Now and Then)
Sam Micelli (Who's the Boss; at least in the early seasons)
Tatsuki Arisawa (Bleach)
Trixie Troubleby (LazyTown)
Toph Beifong (Avatar: The Last Airbender)
Vada Sultenfuss (My Girl)
Vanellope von Schweetz (Wreck-It Ralph)
Winry Rockbell (Fullmetal Alchemist)

Possible tomboys (I'm less sure about)

Beka Cavish (Luck in the Shadows)
Djaq (Robin Hood)
Dolores Rebchuck (Grease 2)
Éowyn (The Lord of the Rings)
Gretta (Dwight in Shining Armor)
Hayley Goodfairer (The Sandlot 2)
Jane Turnkey (Jane and the Dragon)
Jo Lupo (Eureka)
Kate Wetherall (The Mysterious Benedict Society)
Kit Tanthalos (Willow)
Leslie Burke (Bridge to Terabithia)
Lou Davis (Brotherly Love)
PJ Franklin (My Boys)
Sam Puckett (iCarly)