Zero Suit Samus from Brawlgasm is basically a walking version of this trope.
Nobody Dies: When Asuka first gets into her plugsuit as Unit-02's new pilot (it's a long story), Shinji walks by one the way to a test. Once he gets a good look, a wall decides to say hi. Combining this with the multiple situations of Did I Just Say That Out Loud?, it's a wonder that Asuka hasn't gotten over her socialization issues.
Earth and Sky: Happens repeatedly to Apple Bloom around Pipsqueak. Then they hook up, and it starts happening to him.
When Spike gets a good look at Quillina the dragoness in chapter 24, he ends up chewing on his pen and trying to write with a piece of agate he was snacking on.
In The Wizard in the Shadows, Harry is angsting about the oncoming army of Mordor and moans that not even Weasley Wizard Wheezes exploding could distract him. Ginny is wearing a Modesty Bedsheet and takes this is a challenge. Ginny drops said bedsheet.
Naruto:Asunder: Naruto's reaction to Hinata wearing a skintight body suit (He fought of the nosebleed). Not helped by Hinata thinking Evil Tastes Good and teasing Naruto the whole time.
Escape From The Hokage's Hat: While out shopping for new clothes and supplies (they've been out in the wild for 4 months) Hinata asks for Naruto's opinion on her new outfit. What he sees is her wearing a blue version of Tsunade's top with a spandex one piece that stops at mid-thigh at the bottom and shows off her Absolute Cleavage up top. He's quiet for a beat before blurting out how hot she looks.
Nyx's Family: In one scene, Roller Reel — a teenage Crystal pony cameraman Twilight hired to document her research — walks into the room when Twilight is talking to her friends, and gets hit hard with the realization that he's in the same room as what are described in-universe as the six of the hottest mares in Equestria. Not only does he trail off mid-sentence, but all he can focus on is admiring them.
In Alabaster Orchestra, Bazz-B's fight with Hitsugaya is briefly interrupted when he notices Matsumoto's boobs.
Origin Story: Alex Harris is a magically created clone of Power Girl, so what else would you think happens? While Alex expects people, especially men, to react like this, and uses this to her advantage, she can still get annoyed by it.
Tony Stark acknowledges that he has a tendency towards this, and is ashamed to admit that it does interfere with his professionalism. He does try to not be distracted by Alex when he realizes he has been ogling a 17 year old girl.