Angry Birds: Black bird (choleric), white bird (melancholic), red bird (phlegmatic), and yellow bird (sanguine).
The four spirits of the Book of Prophecy in Avalon Code can be identified as this: Rempo (choleric), Ur (melancholic), Neaki (phlegmatic), and Mieli (sanguine).
In Blaze Union, the first five party members: Garlot (choleric), Jenon (melancholic), Medoute (phlegmatic), Siskier (sanguine), and Aegina (leukine). And after the party dynamics suffer an upheaval, things shake down like so: Gulcasa and Leon (choleric), Nessiah (melancholic), Baldus (phlegmatic), Emilia (sanguine), and Aegina is... still leukine.
Borderlands: Mordecai (melancholic), Lilith (phlegmatic), Roland (choleric), and Brick (sanguine).
Borderlands 2: Axton (sanguine with a bit of choleric), Maya (melancholic), Salvador (choleric), Zer0 (phlegmatic). With DLC, there's also Gaige and Krieg, who are Sanguine and Choleric respectively.
Hyperion: Handsome Jack (choleric), Mr. Blake (melancholic), Professor Nakayama (sanguine), Angel (phlegmatic).
Catherine, in terms of Vincent and his three bros that he hangs out with at the Stray Sheep. Orlando (choleric), Jonny (melancholic), Vincent (phlegmatic), and Toby (sanguine).
Melancholic: Hinata, Koizumi, Pekoyama and Gundam.
Phlegmatic: Komaeda, Nanami and Sonia.
The four playable characters of Drakengard, though at times they muddle about with their humors, tend to fall into distinct ones: Arioch (sanguine), Caim (choleric), Leonard (melancholic), and Seere (phlegmatic).
Fate/stay night has Rin/Archer (choleric), Shirou/Saber (melancholic), Sakura (phlegmatic), and Rider (leukine).
Final Fantasy V is the definition of this trope, right down to the characters representing the same elements for each of the 4 crystals. Bartz (wind — sanguine), Faris (fire — choleric), Cara (earth — melancholic), and Lenna (water — phlegmatic).
Final Fantasy IX's first party: Steiner (choleric), Vivi (melancholic), Garnet (phlegmatic), and Zidane (sanguine).
Due to the author being interested with the subject, MARDEK RPG does this. The author believes everyone has a primary and a secondary temperament, though. Perhaps the clearest ingame example is Legion: a construct created by an inventor. It was animated with dark magic, with the inventor saying the incantation - due to his stuttering, though, four souls entered the body instead of one - one for each temperament.
Mass Effect 2 has the starting four. Shepard (choleric), Miranda (melancholic), Jacob (phlegmatic), and Joker (sanguine).
Mass Effect 1 and Mass Effect 3 squads are often comprised this way: Shepard (choleric), Garrus (melancholic), Liara (phlegmatic), and Tali (phlegmatic). Likewise, Ashley (sanguine) and Kaiden (neutral phlegmatic).
Mega Man (Classic series): Forte/Bass (choleric/sanguine), Proto Man/Blues (melancholic/choleric), Mega/Rock Man (melancholic/sanguine), and Duo (phlegmatic/leukine).
Mega Man Battle Network: As it seems at first — Lan and Gutsman.EXE (choleric), Mayl and Glyde.EXE (melancholic), Megaman.EXE (phlegmatic), Yai and her Navi Roll.EXE (sanguine), and Dex (leukine). As it turns out — Dex (choleric like his Navi), Chaud (melancholic like his Navi), Mayl (phlegmatic, like Megaman.Exe), Yai and Roll (sanguine as always), and Lan (leukine).
Mega Man X Maverick Hunters in most distinctive colors: The sensitive, conscientious X (grey, cyan, and blue — melancholic), the Anti-Hero Zero (red and yellow — choleric), the polite and fatherly Signas (white and black — phlegmatic/leukine), and the adventurous wise-guy Axl (red and white, nevermind indigo — sanguine).
The villains: Vile is choleric (and dang!!); Lumine is melancholic; Dynamo is sanguine; and Sigma is leukine.
X-Hunters, counting Vile as the solo X-Hunter in his own right: Vile (choleric/melancholic), Agile (melancholic/sanguine), Violen (sanguine/choleric), and Serges (phlegmatic/leukine).
Capcom never made clear whether classic Mega/Rock Man is the same Mega Man as X. If they are the same, Mega Man underwent a major temperament change. note Some may argue that the melancholic temperament simply got brought to clearer light as Mega Man got infused with human feelings.
Four Guardians, matching their respective colors: The encouraging but Trigger Happy Fefnir (red — sanguine/choleric), the loyal, confrontational Phantom (red and grey — choleric/melancholic), the calm-but-playful Leviathan (white and blue — phlegmatic/leukine), and the reliable and civil Harpuia (green — melancholic/sanguine).
Of the melancholic hero X a duplicate was made, who turned out more choleric than melancholic and not even remotely mature, scarcely one thing like the original X.
Evil trio of Zero 3: With what little personality he's shown to have, Omega seems to be phlegmatic/sanguine (opposite Copy-X); Weil seems to be leukine.
In Temperament, Gandrayda alone fits her respective weapon element (electric — sanguine).
The Beauty and the Beast unit in Metal Gear Solid 4 applies: Raging Raven (choleric), Crying Wolf (melancholic), Screaming Mantis (phlegmatic), and Laughing Octopus (sanguine).
The Cobra Unit in Metal Gear Solid 3 applies: The Pain/The Fury (choleric), The Boss/The Sorrow (melancholic), The End (phlegmatic), The Fear (sanguine).
Nazi Zombies: Tank (choleric), Takeo (melancholic), Nikolai (phlegmatic), and Richtofen (sanguine).
NieR features has something of this as well. Nier (choleric), Emil (melancholic), Grimoire Weiss (phlegmatic), and Kaine (sanguine).
Judging by their programmed natures, the Pac-Man ghosts: Pinky is choleric (chases and ambushes); Inky is melancholic (cautious); Clyde is phlegmatic/leukine (indifferent and random); and Blinky is sanguine (cocky, always chases).
Intentionally invoked in Planescape: Torment. In the end game, you meet up with three copies of yourself, who are the good incarnation (melancholic), crazy incarnation (sanguine) and pragmatic incarnation (choleric). The character of the protagonist depends on how you've been playing him, but he does start out as phlegmatic.
Star Wars: Republic Commando: The four Clone Commandos of Delta Squad are this. Delta-38, "Boss", is choleric, showing good leadership instincts. Delta-07, "Sev", is melancholic, being the Cold Sniper of the group and showing great care to place each round for maximum effenciency. Delta-40, "Fixer", is phlegmatic, being, as Taun We put it, "A pure and uncomplicated soldier." Delta-62, "Scorch", is sanguine, showing much enjoyment in blowing the CIS forces apart.
In Street Fighter II, the four members of Shadaloo: Balrog (choleric), Sagat (melancholic), M. Bison (phlegmatic), and Vega (sanguine).
In the Super Mario Bros. series and its Wario Land spinoff: Waluigi (choleric), Mario (melancholic, but not brooding or depressive), Daisy (sanguine), Yoshi (phlegmatic), Wario (choleric/melancholic), Luigi (sanguine/choleric), and Peach and Toad (leukine).
The ATX Team in Super Robot Wars. At first the lineup is Sanger (choleric), Bullet (melancholic), Kyosuke (phlegmatic), and Excellen (sanguine). Later, Kusuha was drafted into the team as the leukine. Later on, Sanger leaves, and Kyosuke takes on the choleric mantle; and when Lamia enters, she takes on the phlegmatic mantle.
Sanguine and choleric: Luigi, Falco, Captain Falcon, King Dedede
Phlegmatic/leukine: Peach, Link, Samus, Game and Watch, R.O.B., Pokemon Trainer
The Colour Tuesday: Alex is the hotheaded driver of the story (choleric). Kyle is the determined and selfless (melancholic). Bella is a slightly airy Cloudcuckoolander (sanguine). Chadd, the last permanent cast member, is a born follower (phlegmatic).
The Team Fortress 2 classes can be seen throughout the spectrum: Scout (choleric), Soldier (sanguine-choleric), Pyro (sanguine), Demoman (choleric-melancholic), Heavy (leukine, leaning choleric), Engineer (phlegmatic), Medic (phlegmatic-sanguine), Sniper (melancholic), Spy (melancholic-phlegmatic)