The Light Warriors of 8-Bit Theater: Red Mage is sanguine (emphasis on arrogant and self-indulgent); Thief is choleric (emphasis on narrow-minded and obsessive); Fighter is phlegmatic (emphasis on lazy and reactionary); and Black Mage is melancholic (emphasis on independence and perfection).
There are a lot of characters in the Web Animation series The Bear Show, so they have their own Temperaments: Mario, John Cena and Peter Griffin (sanguine and choleric), Randy Orton, Stewie Griffin, Sheriff Woody, Link and Alberto Del Rio (choleric), Luigi, Daddy Bear, CM Punk and Star (sanguine), Triple H and Pikachu (melancholic), Kirby (phlegmatic), and Toad (leukine)
The four main characters of the Web Animation series Broken Saints fit fairly well: Oran (choleric), Kamimura (melancholic), Raimi (phlegmatic), and Shandala (sanguine).
Albeit, Shandala doesn't quite fit any of them, but her bright, cheerful, and compassionate nature recommend her most to sanguine.
An entire episode of the webseries CrackedAfter Hours is devoted to discussing how many famous groups of four adhere to this schema, even describing several groups already listed on this page (though it's worth noting that they have misattributed the sanguine qualities to choleric characters, and vice versa). As they are also a quartet, they even describe themselves (indirectly, through analogy to the Teenage Mutant Ninja Turtles).
By their definition: Michael (sanguine), Dan (phlegmatic), Soren (melancholic), and Katie (choleric).
Cry Havoc features Skoll as sanguine, Karcharoth as choleric, Hati as melancholic, and Fenrir as phlegmatic. These characteristics seem to drive them apart more than unite them, as is normal.
Ctrl+Alt+Del: Ethan (sanguine), Lucas (melancholic), Lilah (choleric), and Zeke (phlegmatic).
Looking at the the questing team in Digger, The Shadowchild (sanguine), Grim Eyes (choleric), Murai (melancholic), and Digger (phlegmatic).
The main fighters from Dragon Ball Z Abridged each fit one or one combination: Goku is Sanguine/Choleric, Vegeta is Choleric, Tien is Choleric/Melancholic, Piccolo is Melancholic, Gohan is Melancholic/Phlegmatic, Krillin is Phlegmatic, Trunks is Phlegmatic/Sanguine, Chiaotzu is Sanguine, and Yamcha is Leukine.
The eponymous doctors of The Dragon Doctors: Sarin (sanguine), Goro (choleric), Mori (melancholic), Kili (phlegmatic), and Aki (leukine). Fittingly, they were also compared by the artist to Air, Fire, Earth, and Water, respectively, matching the Four Temperments' elemental affiliations.
The Dreamer: Alexander (choleric), Beatrice (sanguine), Nathan (melancholic), and Alan (phlegmatic).
Electric Wonderland: Trawn (choleric), NJ (melancholic), Shroomy (phlegmatic), Aerynn (sanguine)
Going by the negative traits (because really, they have no others,) the cast of Exterminatus Now fits pretty nicely: East (sanguine), Lothar (choleric), Virus (melancholic), and Rogue (phlegmatic).
Ruby is Sanguine. She is passionate, energetic, and brave, although fool-hardy and impulsive may be a better description at times. She also has a big, big love of weaponry and that adds more fuel to her happiness and excitement.
Weiss is Phlegmatic. "Calculative" describes nearly every aspect of her character, from how she deals with people to her fighting style. She is also quite the judgmental know-it-all and definitely has a Holier Than Thou demeanor to anyone who have not proven themselves better than herself in her eyes. She is also uncaring to those useless enough to "prove" themselves worse than her.
Blake is Melancholic, largely keeping to herself, and remarkably idealistic (though it may be a bit hidden between the lines) for having such a troubled past. She does not come off as shy and timid, however this is probably more because she is become very good at putting up a front and hiding her feelings (again, due to her troubled past).
Yang is Choleric. She fiercely watches out for and takes care of her sister Ruby and has a Hair-Trigger Temper, literally if her hair gets damaged. Despite this, she is quite optimistic about most people given her immediate initial reactions to both Blake and Weiss.
As for Team JNPR:
Jaune is not much of anything at the moment, but that is part of his character arc — he is probably on track to grow into the Choleric role.
Pyrrha, who has been helping Jaune grow into his role as leader, is clearly the supportive Phlegmatic.
Ren's apparent tranquility pegs him as a Melancholic. He is calm, well-mannered, and just takes care of the task at hand.
The enthusiastic Nora is clearly Sanguine.
The webcomicSacred Pie features phlegmatic leader Roonas, choleric Sid, and a very sanguine Bob.
Sluggy Freelance fits this trope very well: Torg (sanguine), Riff (melancholic), Gwynn (choleric), and ZoŽ (phlegmatic).
The core group of Tales of MU: Mack (melancholic), Amaranth (sanguine), Steff (choleric), and Two (phlegmatic). And Ian and Dee are both strong candidates for leukine.