In Dragon Bones, Ward adapted an inappropriately loud voice as part of his Obfuscating Stupidity. His standard way of greeting someone was to yell their name in a thundering voice, clap their back, and shake their hand with a little too much force. After he drops the disguise, he behaves rather normal.
Stephen Colbert shouted the entire transcript into a tape recorder for I Am America and So Can You!
Harry Potter has a lot of difficulty keeping his voice at a normal volume in Harry Potter and the Order of the Phoenix. Even when he's not in CAPSLOCK!Harry mode, you can make a drinking game out of the number of times Ron or Hermione indicate that he's getting unnecessarily loud for the situation. Semi-justified in that Harry appears to be suffering from a mild form of PTSD (and most likely puberty) and gets frustrated a lot. Also, he keeps picking up on Voldemort's -usually bad- moods.
Gulliver's Travels: Gulliver has to develop this when he was in Brobdingnag in order for the sixty-foot tall inhabitants to even hear him. Naturally, when he got back to England he was still yelling out of habit.
In the The Phantom Tollbooth, Dr. Kakofonous A. Dischord, Doctor of Dissonance, whose middle name is AS LOUD AS POSSIBLE!
Despite not having what we would call a "voice", Visser Three fits this trope to a "T". He seems to have no concept of private thought-speak, and constantly broadcasts everything he says to everyone in range.
Similarly, Jake describes Crayak's "voice" as Crayak screaming at the top of his lungs.
Mr. Men: Mr. Noisy and Little Miss Loud fit this trope to a "T".
In the Jeeves and Wooster stories and novels, a lifetime of fox-hunt halloos has left Bertie's Aunt Dahlia with this sort of voice.
In Men at Arms, one of the recruits for the City Watch is the town crier. His speech is all represented in Caps Lock.
Colon: And who are you? Silas Cumberbatch: SILAS! CUMBERBATCH! Colon: Didn't you used to be town crier? Silas: THAT'S RIGHT!
In The Last Continent, it is mentioned that Archchancellor Ridcully "spoke as loudly as most people shouted."
While the voice of DEATH is also represented in Caps Lock, he's a subversion of this in the actual novels as it's mentioned that you "hear" DEATH inside your head, rather than with your ears. However, because that's just not possible in something with an audio component, audiobooks and movies of the books give DEATH the loudest and deepest voice they can possibly find, making him an actual example of this trope.
Miss Honeybear in The Berenstain Bears Go to School is described as having a loud, jolly voice. In fact, her quotes end with an exclamation mark.
Same goes for Mrs. Grizzle in The Berenstain Bears and the Sitter. She is also described as having a loud, jolly voice.
Mr. Howell, the strict teacher in the Origami Yoda series, has this. Being a strict teacher, he loudly yells at students who misbehave, and even those who don't misbehave.
Ivy Carson in Zilpha Keatley Snyder's The Changeling is described as having a loud, clear voice. When Martha first hears her, she expects the teacher to say something to her about using a "good classroom voice."
In Mirabile, Leo raises an alien "bird" from the egg and names it Mabob (short for "Thingamabob"). Mabob turns out to have a hundred-plus decibel GRONK! which he lets loose every time he's excited about something, indoors or out. After the first time he does it in a vehicle while she's driving, Annie makes it a priority to teach him about "indoor voice".
In Second Apocalypse Wutteät, the father of dragons, whom Achamian encounters in the ruins of the library of Sauglish, spits out his entire dialogue VERY LOUDLY. The fandom even jokingly calls him ALL-CAPS DRAGON.