1. Crash (2004)
As any randy teenager in a slasher flick could attest, sex of any kind around cars is a bad idea, since it implies a secluded venue away from the prying eyes of everyone but the psycho killers, and for some reason, psycho killers really hate it when teenagers have sex. But even leaving that sex-equals-death slasher-movie cliché aside, oral sex in or around cars seems to be a particularly bad idea in film. And not just for trashy teens. Even in a mainstream movie like 2004's Oscar-winner Crash, even for upscale, married black professionals, a woman with her head in her husband's lap at the wrong moment is at heavy risk of being pulled over and sexually molested by a racist cop played by Matt Dillon, kicking off a chain of ugly and artificially symbolic events.
2. Parenthood (1989)
On a lighter note, in Parenthood, oral sex in a moving vehicle leads instantly and directly to a car crash that's played for laughs. Concerned that her husband Steve Martin is too tense, Mary Steenburgen attempts a relaxation technique that her sister-in-law apparently swore by back in college. Cut to Martin and Steenburgen standing by their wrecked car, with her apologizing, and him explaining that she just took him by surprise. When a cop approaches and asked how the accident happened, Martin snaps "Show him, honey!"
3. Legal Eagles (1986)
Something similar happens in Ivan Reitman's Legal Eagles, though it's a minor, offscreen incident discussed by two lawyers, notable entirely for the language used to describe it. A colleague of Robert Redford's asks whether he should be able to blame his client's car crash on the woman who was "resting her head in his lap… actively." When Redford demands an English translation, the other lawyer tries again: "Resting her head with affection. Ultimately, the accident is her fault, and not his. What do you think?" Redford answers, "I'd sell the screen rights."
4. Thinner (1996)
When administering fellatio to your husband while he's driving, it might be wise to consider the movie rights, but it's also wise to consider whether he might get distracted and run over a gypsy woman whose irate father has magical powers and a vindictive sense of poetic justice. For obese lawyer Robert John Burke, a gypsy curse proves a surprisingly effective alternative to conventional diets. Given the size of his unconvincing pre-curse fat suit, though, it's hard to imagine how his wife managed to get in there to distract him in the first place.
5. Legend Of The Overfiend (1989)
Admittedly, no one having sex in this legendarily violent, supremely graphic anime really comes out well. But one particularly memorable sequence involves a speeding hot rod and a pumped-up, far-too-excited driver with a woman who's actively engaged in keeping him excited. It also involves a gigantic demon-creature who sees to it that they get a fiery, explosive comeuppance for their unsafe vehicular operation.
6. Monster (2003)
Somewhat similarly, no one having sex in Monster really comes out unscathed. But serial killer Aileen Wuornos (played by Charlize Theron, who won an Oscar for the part) is particularly scarred by her work as a hooker specializing in administering blowjobs to blue-collar workers in their vehicles. When one of those encounters goes violently wrong, she ends up killing her john to save herself, thus starting a murderous spree that closely resembles her previous prostitution work, except with less fellatio at the end of each encounter, and more shooting.
7) Natural Born Killers (1994)
The most memorable oral-sex scene in Natural Born Killers happens on a car rather than in one, but the principle remains the same. After inviting an excitable young stranger to go down on her on the hood of a Corvette, Juliette Lewis takes issue with his technique and shoots him dead, snarling "That's the worst fucking head I ever got in my life! Next time, don't be so fucking eager!" Uh, next time?
8) The World According To Garp (1982)
But the definitive example of why oral sex and cars don't mix happens in the film adaptation of John Irving's The World According To Garp, when Garp (Robin Williams) pulls into his own driveway and crashes into another car. Unfortunately, his wife is in that other car, resolving a conflict with her lover in a direct fashion. She loses some teeth; her lover loses most of his penis, which is in her mouth at the time of the crash. Suddenly, that secluded tryst in psycho-killer-filled woodlands starts to sound good by comparison. As Garp transsexual John Lithgow mourns, "I mean, I had mine removed surgically under general anesthesia. But to have it bitten off in a Buick!"