Muruta Azrael belts out a big "YATTAAAA!" in Mobile Suit Gundam SEED (dubbed into a Big Yes).
In context, this is because he's just found the means to commit mass nuclear genocide.
In Castle in the Sky, one of Dola's boys, Louie, as voiced by Mandy Patinkin, gleefully shouts this after Dola agrees to let Pazu and Sheeta accompany them. He follows this up with a "No more swabbin' the decks! Hooray!"
Hajime No Ippo: A big "YATTAAAAAA!!" is pulled by Ippo after he wins the japanese title.
In Bakuman。, the typical response of Mashiro and Takagi to getting serialization.
In Happy Yarou Wedding, Shouta gives several of these combined with a Happy Dance when he thinks Yuuhi's going to become his mama, and again when he learns Yuuhi will move in.
In The Legend of Total Drama Island, Lindsay has been tasked with giving her friend Sadie a bad haircut during the phobia challenge, and cuts loose with a Big YES when she realizes that she can use extensions to do a reversible job.
Masterminds, toward the end of the movie, when the Big Bad, played by Patrick Stewart, sees a light at the end of the tunnel, he assumes he's escaped, and lets out a series of increasingly larger Big Yes-es. Then he sees what actually lies outside the tunnel, a long drop into a sewage canal, and lets out a Big "NO!".
In Home Alone and Home Alone 2, Kevin would often drop a gleeful "YES!" after inflicting his latest amusing injury on Harry and/or Marv.
In The Fifth Element, the David character screams "YES!" when Leeloo finally stops Mr. Shadow and saves the universe.
Max in Yellow Submarine, after the Chief Blue Meanie decides at the end that if you can't beat 'em, join 'em:
Max: ''Yyyyesss, your Newness!
In Scanner Cop II, Volkin gives one after he absorbs the psychic energy from his first two victims.
If You Believe: Susan is a jaded editor, slowly overcoming her depression and burn-out syndrome. When she phones her biggest star of a writer and learns that his Writer's Block is over, she jumps and starts dancing. She keeps chanting multiplied and somewhat toned down "Yes! Yes! Yes! Yes! Yes!". She's kind of embarrassed when her new writer Tom Weller sees her. He thinks she's cute.
In Reaper Man, Azrael answers Death's request for more time with a big "YES." Literally big, that is; it's in an extremely large font size. According to Terry himself, it was supposed to be near the top of a left page, so that it would surprise the reader when they turn the page, but not all printings did this.
Harry Kim in the Star Trek: Voyager episode "Timeless" shouts this (here at 9:03) when he successfully sends the code to collapse the slipstream into the past, preventing Voyager's crash before the Delta Flyer exploded.
In the Family Matters episode "A Thought in the Dark", Steve belts out "Yes! Yes! A thousand times yes!" when Laura invites him to come along with her to a Dave Koz concert, thinking that she's finally given in to his romantic overtures after a steady string of rejections. She isn't - it's actually a prelude to a double-date where Laura is trying to set Steve up with Myra, a cousin of one of Laura's Guys of the Week.
Midshipman Hether gives a Big "Yes!" when Archie tells him and other middies (Horatio and Cleveland) that they are being transferred to the Indefatigable under Captain Pellew. It's complete with jumping excitedly from a chair and cheerfully hitting the ship's ceiling.
Styles rejoices with moderately big Big "YEEES!" as Matthews informs the crew that Mr Hornblower survived his dangerous task in "Retribution".
How I Met Your Mother has Barney giving some news that the rest of the cast (and audience) react favorably towards, when he reveals yet another video selection from Robin's embarrassing past as a Canadian Teen Pop Star:
Roddy Piper: "Will you accept his challenge, Yes or No?!"
Hulk Hogan: "YEEEEEEESSSSSSSS!!!!!!!!"
When Daniel Bryan won the World Heavyweight Championship in late 2011, he celebrated his wins, be they non-title or otherwise, by repeatedly screaming, "YES! YES! YES! YES! YES! YES! YES! YES! YES! YES! YES! YES!"
The chant has hit Yankee home games and went over big time in London. The YES! YES! YES! shirts were placed on back order due to demand. It's becoming an Ascended Meme that WWE has been forced to recognize.
His finisher is also now referred to as the YES! Lock.
The sound effect for leveling up in TaskMaker is a Big Yes
In Pokémon Mystery Dungeon: Gates to Infinity, when you accept your partner's request to build Paradise, the place that your partner wishes to create, your partner lets out a Big Yes and then, after some dialogue, he offers you to nickname him, which will be your partner's name throughout the entire game.
Video Game/Dragonfable has one in the Final Showdown after Nythera asks a question.
Along the same lines, in the Galaxy Rangers episode "Shoot Out", the Queenof the Crown was on her feet cheering when she had three Rangers in chains and the fourth had been shot.
Megatron of Beast Wars was quite fond of a more refined version of this, yeeesss.
And while we are on the subject of Transformers, we probably should include Optimus Prime from Transformers Animated as he does this while testing out a jetpack for Ratchet towards the end of season 3.
Duff Man from The Simpsons usually shouts "OH YEAH!" whenever he appears.
In another episode, Homer broke Lisa's heart by betting on her loss in a crossword contest. He does give an appropriate Big "NO!" when she says she'd no longer be his little girl, but gives an equally appropriate Big Yes when asked if he wants to buy band chocolates 3 seconds later.
There's also the man who usually says "YEEEEEEESSSSSSSSSSSS!" to questions. When a mildly creeped-out Homer asked him "Why do you talk like that?" he answered, "I had a strooooooooooooke".
A Big Yes turns into a Big "NO!" very quickly for Jafar in Aladdin when he thinks he has the lamp but then checks his pockets and realizes Abu stole it. And then the exact same transition after his wish to become a genie is granted, before finding out he is bound to a lamp. Not to mention Aladdin himself, after his first kiss.
In an episode of Total Drama World Tour, Tyler gets one of these when Lindsay finally recognizes him and remembers his name. Of course, being that they're in the Alps at that time, he causes an avalanche.
Parodied on MAD with the X Meets Y parody CSiCarly (a crossver between CSI: Miami and, of course, iCarly). It turns out that the YEEEEEAAAAAH!!! is actually coming from Horatio standing on Freddie's foot.
In the My Little Pony: Friendship Is Magic episode "The Cutie Mark Chronicles", Twilight Sparkle does this during her flashback when Princess Celestia offers to personally tutor her in magic, excitedly shouting "Yesyesyesyes!" over and over again as she jumps for joy. After the cut back to present day, we see Twilight has apparently gotten a little too caught up in her story and is doing this in front of the Cutie Mark Crusaders.
Rarity does it in "The Ticket Master", when talking about what she would do if her Prince Charming proposed to her: "Of course, I would say... YES!!!"
Her sister Sweetie Belle does on in "Heart and Hooves Day" when Cheerilee finally asks Big Macintosh to be her very special somepony. Many have noted that her "YES!!!" sounds a lot like Rarity's. See foryourself.
Inverted in "Sonic Rainboom", in which Rainbow Dash tries to teach Fluttershy the "elements of a good cheer". She's hoping that she'll cheer her on at the Young Flyers Competition, but since Fluttershy is a Shrinking Violet...*BIG INHALE* Yay. Later played straight when Rainbow Dash actually does manage to pull off the Sonic Rainboom, causing her to scream "A SONIC RAINBOOM! SHE DID IT! SHE DID IT!"