Many aliens and droids in Star Wars are unintelligible, speaking only in beeps, growls or alien speech. R2-D2 and Chewbacca are both examples. Almost everyone can still understand each other, leading to a lot of Bilingual Dialogue. However, there are occasional instances where characters will translate for each other. Examples include the two cantina ruffians and C-3PO's stint as a translator for Jabba the Hutt.
C-3PO is a "protocol droid" designed to help with interspecies communication. This means it's his directive to translate between various languages (of which he knows a lot), and he does it quite often.
Captain Stimpson in Texas Across the River is capable of speaking normally, but whenever he issues a command, it sounds like, "Haroo, har!". His soldiers invariably follow the command, despite themselves being unable to understand what he's saying.
Gabby Johnson of Blazing Saddles speaks "authentic frontier gibberish":
"..And no sidewindin', bushwackin', hornswagglin' cracker croaker is gonna rowway... bushescutter!"
"Now who can argue with that? ...I think we're all indebted to Gabby Johnson for clearly stating what needed to be said!"
Whisper in Live and Let Die. Due to some unspecified condition, he's unable to speak above a whisper.
Mikey O'Neil in Snatch speaks with such a thick "Pikey" accent that outsiders have difficulty understanding him. His subtitles occasionally revert to "??????"
Mumbles in Dick Tracy, played by Dustin Hoffman. A stenographer is seen giving up entirely on translating. Tracy is able to discern what he's saying by recording him, and then playing back the tape slowly.
After which of course, Mumbles is able to speak coherently to confess Big Boy Capri's plans. Albeit, he's still mumbling slightly and speaking kind of fast.
Police Constable Bob Walker of the Sandford Police Service in Hot Fuzz speaks with such a thick rural accent that Nicolas Angel needs other villagers to translate for him. However, isolated country folks are unintelligible to everyone but Bob, forcing a translation chain. Interestingly, as Angel gets more familiar with the town, Bob's dialogue becomes more intelligible.
Fenster in The Usual Suspects. Benicio Del Toro invented this character aspect because the character was too thin, and existed only to die. He based his performance on Dustin Hoffman's performance as Mumbles. Cast members were asked to have him repeat himself if they couldn't understand his line delivery. A few of these end up in the final cut.
Hilariously played with in Hunchback Of Notre Dame by Disney. The heroes are caught by the thieves, tied, gagged, mock-trialed and are about to be hanged.
Clopin: Any last words?
Quasimodo and Phoebus:[mumble incomprehensibly through their gags]
Clopin[condescendingly]: That's what they all say.
Farmer Fran in The Waterboy has a completely unintelligible Cajun accent.
Frenzy in Transformers live-action film speaks almost entirely in Cybertronian. However, he does speak English sometimes, such as his last words: "Oh, shit." Shockwave from Dark of the Moon is also fairly hard to understand.
Blaine Cody from Rat Race, due to a self-made tongue piercing. His brother, Duane Cody will sometimes "translate" his speech.
The eponymous Pootie Tang. It is said that he is too cool for words and nobody undestands what he says, but what he means.
Herbie The Love Bug embodies this in that his horn is his only method of communication. At least one person from each movie understands him.
Played with in Enchanted as far as understanding The Unintelligible goes. When Pip enters the human world, he finds himself in the difficult position of only being able to utter word-like squeaks. Prince Edward thinks he understands him perfectly. He doesn't.
Gymnasia in A Funny Thing Happened on the Way to the Forum. A woman hailing from the Isle of Silent Women, she expresses with pantomimes apparently unrelated to whatever is happening. When Pseudolous, her Love Interest and Butt Monkey reveals her pantomimes as an highly organized sign language which he's able to translate to the audience, the rest of the cast is genuinely suprised.
Elmo in Schizopolis speaks in a weird, drawling language that includes such expressions as "Arsenal! Nose army," (a greeting), "throbbing dust expression" (roughly, "nice place"), and "ambassador landmine" (roughly, "let us copulate"). When compelled to speak in normal English, he becomes almost psychotically frantic.
The titular protagonist in Spider is a paranoid schizophrenic who mumbles his words incoherently much of the time.
Q*bert in Wreck-It Ralph speaks in garbled syllables accompanied by speech bubbles, as he does in his games. Felix can at least talk back though "[his] Q*bertese is a little rusty".
insectosaurus from Monsters vs. Aliens only speaks be making a screeching noise. It also appears that only Missing Link can understand him.
Jack The Giant Slayer :Fallon's smaller head's speech is almost entirely incomprehensible.
