In a strange in-joke, there's a "cursor" pun in The Muppet CD-Rom: Muppets Inside, which features a Whatnot wandering past the Databus, muttering "Ahh, the dirty little frazbasset grummelslinger, the little shrooby rooby..."
Murray in Sly 2: Band Of Thieves. The combination of spice and hypno-boxes slowly made this happen, until he mindlessly roared and charged at Sly.
Team Fortress 2: In the "Meet The Spy" video, this is the BLU Scout's reaction to seeing pictures of the RED Spy with his mother. Or rather, this is the RED Spy's (actual) reaction to seeing that the BLU Spy got hold of pictures of him with his "petit chou-fleur". Or both.
Kirby Super StarUltra. Revenge of Meta Knight. Heavy Lobster. Paint Ability. When you hit Heavy Lobster with it, its entire body gets covered in paint and its eyes stop working, causing it to flail around erratically. The crew of the Halberd subsequently break into angrish trying to comprehend how easily Kirby destroyed the giant shrimp mech.
Captain Vul: Rassa frassa blassa! Arrrgh!
Mitsunari from Sengoku Basara is usually pretty good at coming up with gruesome and imaginative death threats, however when enraged his inspiration fails him and he starts yelling "I'LL KILL YOU!" over and over again.
In the Thief games, if you are being chased by a guard and you climb or jump to somewhere they can't follow, their immediate response is pure, incoherent Angrish in frustration at you escaping.
In Mass Effect 1, when Saren hears Shepard made it to the beacon on Eden Prime, he freaks out, stomping around the control room and sputtering incoherently. It's actually Sovereign that's pissed off, and acting through Saren, but has the same effect.
Saren (subtitles): Argh! Grr! Rahr!
Decidedly not played for comedy in Asura's Wrath. When Asura gets mad (and we mean truly mad, as in transforming into Berserker and Wrath modes), he can't form coherent sentences and expresses himself through pure murder and violence. Also inverted in the first DLC episode; when Chakravartin kidnaps Mithra, Asura flies into Wrath mode, where he was previously unable to speak, but he manages to form a few coherent sentences when speaking to Mithra while trying to bash through the barrier holding her.
In Borderlands, using Brick's Action Skill, "Berserk", will sometimes cause him to scream incoherently as he rushes toward his enemies, punching them. The same goes for Krieg in the second game, whose dialog is generally a mix of this and nonsensical phrases involving meat or blood.
Inverted in Borderlands 2 in the case of the Goliaths, who upgrade from Hulk Speak and actually become more eloquent and...vivid as they're consumed by their rage once you knock their helmets off. They're still sputtering fountains of rage, but they can at least speak complete sentences at that point.
Earthworm Jim; Jim does this if you lose one of between-level races with Psy-Crow (which means you have to fight him before proceeding to the next level), and also at the Game Over screen.
In Commander Keen 1 there are several martian churches, where you can receive telepathic messages from the saints. In one of the churches the saint is a Garg (a species of martians consisting of a large mouth with eyestalks, who hate basically everything) and the telepathic message is: YOU HEAR IN YOUR MIND: GAAARRRRRGG!
In Dangan Ronpa, when Makoto Naegi, the protagonist, manages to figure out who the first culprit is, the first culprit freaks out and starts screaming "AHO AHO AHO AHO AHO AHO AHO!" repeatedly, which translates approximately into, "RETARDED RETARDED RETARDED RETARDED RETARDED RETARDED RETARDED!"
One of the early missions with Trevor in Grand Theft Auto V involves him becoming so angry most of his dialogue consists solely of "AAAARRRGH!" and variations thereof.
In Bravely Default whenever Edea gets especially angry her sentences can be either be preceded or followed by "Mrgrgr!" to the point that it almost doubles as a verbal tic.
Pester the Grox too much in Spore and they scream at you.