The Break-Up. Gary (Vince Vaughn) is watching a boxing match on TV. Brooke (Jennifer Aniston) walks over, goes to the fridge, gets a drink and walks back to her room all while naked. Cue the trope.
In the sequel to National Treasure, Riley Poole is holding a bag full of indiscriminate (but obviously breakable) objects when a pretty girl walks by and asks for his autograph. He's so excited that he's finally recognized as himself (rather than as The Lancer to Ben), and a girl is actually paying attention to him, that he drops the bag immediately.
The Matrix has one of the most memorable examples in the "Woman in the Red Dress" scene. Morpheus and Neo are walking in a crowded part of the Matrix while Morpheus is instructing him that they can't trust anyone still plugged into the system. Neo is distracted by a gorgeous woman who strolls by in a red dress, and when Morpheus asks if he was paying attention and Neo looks back at her, she's turned into an agent about to kill him. Morpheus freezes the program, reveals it to be a test, and points out the message: Agents can be anyone.
Memoirs of a Geisha has a scene with the Mameha (Michelle Yeoh) teaching the protagonist, Sayuri (Zhang Ziyi) that a true geisha can stop a man with her eyes. She demonstrates and then asks Sayuri to do so, which Sayuri does to a passer by riding a bicycle, causing him to crash.
The Naked Gun: In the second film, Frank fights an assassin who has come to kill Jane (who is in the shower). She hears the ruckus and pulls open the shower curtain to see what's up, whereupon both Frank and the Assassin stop in mid-grapple to stare.
In Desperado, Salma Hayek's character, Carolina, is introduced by having her cause an accident at an intersection while crossing the street. She just smiles and keeps on walking.
A trailer for So Fine, a movie about someone who invented bottomless jeans, solely featured the various accidents befalling men who saw a woman walking down the street in them.
Happens briefly in It's a Wonderful Life. At one point, a nameless background male character turns his head to watch Violet walk and nearly gets hit by a car as a result.
In A Fish Called Wanda, barrister Archie Leach is so smitten by Wanda that he leaves his briefcase on top of his car as he drives off.
10: Dudley Moore is so distracted when a car bearing Bo Derek drives by that he drives right into another car. A police car.
Even suave superspies aren't immune to it. In the Get Smart movie, Dwayne Johnson's Agent 23 is a paragon of what an agent should be. Yet he walks straight into a support pole when the sexy secretary smiles at him.
When Max and Agent 99 make the parachute drop into Russia, they are able to go unnoticed by the air marshal on-board because he's busy flirting with a female flight attendant.
Agent 99 using the Show Some Leg trick to get into a fancy party uninvited.
The old Cheech Marin film Born In East L.A. had a couple of gags where an especially attractive Latino woman (who was one of Cheech's garage customers in the movie) would make everyone else stop in their tracks and stare whenever she walked past.
A rather serious example happens in Crocodile Dundee. While in the Outback, Sue convinces Mick to let her go out for a walk alone to prove to him that she can. He follows along from a short distance, because he doesn't think it's safe. Eventually, Sue gets a little careless and spellbound by the scenery, and strips down to her thong bathing suit by a pool, and Mick is a little distracted, bumping his head on a branch. (But fortunately not too distracted, as his concern turns out to be truer than he thought; a crocodile tries to grab at her, and he has to leap to her rescue.)
This happens a lot around Elvira, Mistress of the Dark, particularly in her movies. Men will often forget what they are doing just to get a look at Elvira and her... uh... assets. Some have even died while distracted by her sexiness.
The Police Academy gym is a dangerous place to be while Callahan is working out.
Back to the Future Part 1, when Marty McFly gets distracted by sexy women... while his girlfriend is right next to him.
Occurs during Bad Teacher when Elizabeth is seductively dousing herself in water and rubbing herself across a car when trying to raise money.
Happens at the beginning of Hot Shots! Part Deux where an attractive woman arrives to a Buddhist monastery where Topper Harley is hiding in order to recruit him for a rescue mission. A monk falls into a well while walking and staring at her. Later on, all monks line to up to show off their manliness.
A secretary (identified as such in the credits, the only female cast member listed) walking through the warehouse in Forklift Driver Klaus distracts the male workers enough to set off the final series of accidents resulting in the title character's death.
In the opening sequence of The Longest Day, a pair of French resistance fighters are smuggled past a German checkpoint hidden in a haycart, with a gorgeous woman wearing a skimpy peasant outfit making sure the guards don't pay too much attention to it.
Subverted in Fantastic Four where it appears that Reed is staring at Sue in her skin-tight outfit, but then ...
"Wow! Fantastic! Material made from self-regulating unstable molecules!"
In The Mask, this is why Cameron Diaz's character is sent to meet the nerdy Stanley Ipkiss (Jim Carey).
Also happened for real while filming; apparently, the first time Scarlett Johansson walked onto the set in her Spy Catsuit (which was so tight she was forced to go commando), the film crew mysteriously fell silent.
The professors have this problem around Honey Swanson in A Song Is Born.
The Living Daylights. To distract Pushkin's bodyguard after an alarm is sounded, Bond forcibly strips Pushkin's girlfriend to her waist and has her stand topless facing the door as the guard enters. The guard walks in on the now topless woman, allowing Bond to get the drop on him and disable him.
This actually comes up quite a lot in Bond movies, especially invoked with the lead Bond Girl.
Special mention must go to Vesper Lynd and her purple dress in the 2006 Casino Royale. Bond intends for her to enter behind him to distract his opponents from their cards. Instead, due to their Belligerent Sexual Tension up to that point, she decides to enter in plain view right in front of him, distracting him along with everyone else in the casino.
Mathis: I suppose I don't have to tell you how beautiful you look. Half the people on that table are still watching you.
In Jackie Chan's Chinese Zodiac, JC's attractive female assistant distracts some border patrol guards by getting out of her car to ask where the toilet is, showing copious amounts of leg while at it.
In Weekend at Bernie's, shortly after Bernie's death, a young, blonde, busty woman comes into his house wearing a teeny bikini and asks the two male protagonists if they've seen Bernie. (She wants to know if the beach party is still on.) She has no idea that they - and the audience, most likely - are staring at her. (They clearly aren't used to beachgoers who dress like that.)
In What Planet Are You From?, a woman walks into a bank wearing a white dress that looks like a net, making her underwear visible. The employees start tripping and bumping into things.
In Rat Race, a woman flashes her breasts at the two brothers, causing them to crash their car.
In The Lucky One, Beth is washing dishes when she looks out the window and sees Logan working in the yard. She's so distracted that she's scrubbing the same pot over and over again until her grandma snaps her out of it.
In Just My Luck, Ashley is doing laundry when Jake takes his shirt off in the other room. She's so distracted that she pours an entire box of detergent into the machine without noticing.
Swordfish. After Stanley sees Ginger bathing topless, he bumps into a table when he leaves.
In Mirror, Mirror, Prince Alcott keeps getting robbed and his clothes stolen. Snow White stares at him the first time. The Queen eventually screams, "Oh my God, can someone please get this man a shirt so I can concentrate!" Prince Alcott also gets distracted by Snow White in a lovely dress.
In Wargames, David can escape his holding cell because the guard is coming onto the secretary.
Part of the Rube Goldberg Hates Your Guts scene in Ink involves a teenage skateboarder crashing into another person because he's distracted by the cleavage of a woman bending down to pick up some flowers.
We're the Millers: This is how Rose manages to get the drop on Pablo and save her "family" from being executed.