Raye/Sailor Mars in Megami33's Sailor Moon Abridged has a voice like a shrieking harpy, as well as being an Emo, Satanist, masochist, and generally Ax-Crazy. These traits combine somehow to form the fans' most popular character. You might want to turn down the volume during episode 7, if you value your eardrums.
Lelouch from ''Code MENT can sometimes be like this.
Lelouch: DON'T TOUCH MY STUFF!
From a later episode:
Lelouch:NO! NO! I'm not upset! I'm not! This whole country is upset, with absurd prices! Five dollars for a meal at McDonald's?! I need more meat in my diet! …I look around and I see just stupid! Quit complainin' about religion! No one cares!! Oh boo-hoo, you're gay, you're lesbian, you're straight; MY PENIS DOESN'T WORK!!
In a spoof of 300, United 300, the parody Leonidas definitely qualifies. Lampshaded when King "Jerxes" [sic] asks him why he shouts so much.
Leonidas:I'M NOT YELLING. I'M JUST PASSIONATE.
Randy Hayes of My Way Entertainment is pretty much the poster boy for this trope, but it actually isn't annoying, it makes the ridiculous things he's saying even funnier.
Randy:HATTE MOTHERFUCKIN' KUDASAAAAIII!
Cornelius Fudge and Dolores Umbridge (or "Cornelia Fuck" and "Doris Rumbridge") in My Immortal. Cornelius ends every sentence with an exclamation mark and Dolores says everything in all capitals.
Deserving, so very, very much. Barely a chapter goes by without at least one character yelling.
Midnight Green is deaf to his own powerful voice, and casts a spell to keep it to normal levels. When he deactivates the spell, this happens.
Lord Eden in The Tainted Grimoire. Technically, he does have an indoor voice but the quietest possible is the normal volume for an average person and when addressing large groups, his voice needs very little assistance.
Calvin & Hobbes: The Series has Dr. Brainstorm, spends at least 3/4ths of his dialogue shouting at someone. Calvin himself takes on the role while angry or tired (the latter shown in "Nighty Shut Up!").