Two Girls and a Guy

Three friends from childhood. A girl, her best friend and her best male friend. Is it too much to ask for no drama?

Yes.

The main girl is The Hero, and is usually an Audience Surrogate. Whether or not she's an Action Girl, or a Cute Clumsy Girl, or the Girl Next Door, she'll be easy to relate with. The other girl will usually be the opposite from her in some way in personality or looks. She isn't The Rival, usually. That's usually saved for another girl who's the main villain, maybe the Alpha Bitch or a Dark Action Girl. Tomboy and Girly Girl or Red Oni Blue Oni combinations are common with this pairing.

The guy in the equation is usually friends with both of the two girls or knows them. He is often a childhood friend of both of them and has different interactions with the both of them. He may be just a friend.

Very much susceptible to the Love Triangle, if romance is in the equation. Whether or not the guy is in love with The Hero or The Lancer is usually up to the particular show. There may be a Cat Fight that might ensue, but usually there's more tension amongst the trio then anything. Expect a lot of Shipping Wars and Die for Our Ship as to which girl ends up with the guy.

Compare Three Amigos, where the protagonist is usually male; see also Two Guys and A Girl.

Anime

 * A "switched places" variant on Macross Frontier in the form of "A Guy and Two Girls": Alto, Ranka, and Sheryl.
 * In the early seasons, Magical Girl Lyrical Nanoha had Nanoha, Fate, and Yuuno as the core cast. Atypically, Fate and Yuuno were Nanoha's love interests.
 * IGPX: Takeshi, Amy, Liz. A rare example where the one male is The Hero.
 * Neon Genesis Evangelion has the initial Three Children: Rei, Asuka, and Shinji.
 * While Tenchi Muyo is your typical harem anime comedy, the tension is mostly centered on the main Love Triangle of Tenchi, Ryoko, and Ayeka.
 * No matter the version of Cardcaptor Sakura you go after, there'll always be a girl rounding out the group with Sakura and Syaoran (Kero-chan notwithstanding): if you go for the manga, Tomoyo's always there with them, but in the anime, Meiling is added to the equation.
 * Those Who Hunt Elves: Junpei, Ritsuko, and Airi.

Comic Books

 * Scott Pilgrim: Scott, Kim Pine, and Ramona Flowers.
 * Strangers in Paradise starts out like this, but it gets... complicated.

Live Action TV

 * Hannah Montana: Miley, Lilly, and Oliver.
 * Lizzie Mcguire: Lizzie, Miranda, and Gordo.
 * I Carly: Carly, Sam, and Freddie (pictured).
 * ANT Farm: Chyna, Olive, and Fletcher.
 * That's So Raven: Raven, Chelsea, and Eddie.
 * Hikonin Sentai Akibaranger: Like the Macross Frontier example above, Nobuo, Mizuki, and Yumeria.
 * Naturally Sadie: Sadie, Margaret, and Rain.
 * Buffy the Vampire Slayer: Buffy, Willow, and Xander.
 * True Jackson, VP: True, Lulu, and Ryan

Video Games

 * If you choose the female in Pokémon Black and White, you have female player, Bianca and Cheren.
 * In Katawa Shoujo, main character Hisao can date one of five girls, each of whom has a best friend who often shows up during her route. The possible "two girls" are Lilly and Hanako, Rin and Emi, and Shizune and Misha (who does not have a route).
 * Disgaea has Laharl the prince and two girls, Flonne and Etna.

Western Animation

 * Braceface: Sharon, Maria, and Connor.
 * Though in the episode "The Pickford Project", Connor was bitter about not having any guy friends and was paired with Alden and Brock. By the end of the episode, Connor's happy with the friends he's got.
 * Kim Possible, Ron Stoppable, and Monique (even though she isn't a main character).
 * Cyberchase: Matt, Jackie, and Inez. Your Mileage May Vary on which girl is the main girl; they get equal screentime and treatment.
 * Wonder Pets has Tuck (a male turtle), Linny (a female guinea pig), and Ming Ming (a female duckling).