As compiled by film critic Roger Ebert on his site.
Fountain of Youth
Whenever a childless male is forced to change a diaper for the first time and the infant is a male, the infant will inevitably and energetically urinate on him.
Licking the Llama
When a comic actor makes out with an extremely beautiful person, the kiss is often revealed to be nothing more than a dream sequence, and in fact the actor is being licked by a slobbering animal.
Getting In Shape
In any movie where an athlete must raise himself to another level, there is always a scene in which he/she is seen working out in preposterous ways. This may involve running through crowds that throw fruit at you (Rocky), having champagne glasses set up on hurdles (Chariots of Fire) or balancing on the bow of a rowboat in the ocean (The Karate Kid).
During a chase on foot, if a bus, or any other vehicle longer than a van comes between the chaser and the chasee, the person being chased will magically disappear, thus leaving the chaser dumbfounded.
SNL Grandma Rule
In a surprising number of films featuring former cast members of "Saturday Night Live," the main plot device involves saving Grandma or another older person from losing her house, livelihood, etc. See The Blues Brothers, Happy Gilmore, Dirty Work, etc.
Scene where the audience is expected to believe that two characters can carry on an entire conversation where one thinks theyre discussing something like mathematics or banking, but the other thinks they're discussing sex. See Milk Money, Frozen Assets, every episode of "Three's Company."
The gathering of a loose affiliation of stock players, friends, relatives, star wannabes, hangers-on and professional acquaintances making cameo appearances under the vague notion that a movie is being made. At best, the host is Robert Altman and the end result is art (Nashville, The Player). At worst, the host is Andy Warhol and the result is junk (Lonesome Cowboys). Usually the host is like Burt Reynolds and the result is low-brow entertainment (Smokey and the Bandit).
No. 42 Crosstown Expedience Route
The bus that runs directly between where the characters are and where the scriptwriter needs them to be, every day of the week, at any time of day or night.
Antiques Of Death
Straight razors, ice picks, paperweights, fireplace pokers, meat cleavers, crowbars, dueling pistols, ceremonial daggers, swords, sabers, battle-axes, giant marble ashtrays and other archaic, cliche weapons of mayhem that always seem to be handy for movie murders, even though few homes might actually have any such antiques readily available for an impromptu killing.
Whenever movie characters are seen blissfully riding a bicycle with eyes closed and arms outstretched like angels wings, there is a strong likelihood that they are about to collide with a massive object and be killed.
Fruit Cart Scene
An ancient tradition. Any vehicular chase sequence must involve the upturning or smashing of a cart of fruit, such as one would find along a street or in a farmers market. These crashes precipitate much strategic leaping by merchants, shoppers, and other pedestrians (played by stunt persons) who fling themselves out of harm's way in the nick of time.
Geek Ego Effect
Exemplified by the Dennis Nedry character in Jurassic Park, this describes the maniacal behavior of the mandatory overweight nerd with thick glasses, pen protector, and an I'll-get-even-with-the-rest-of-the-world-for-not-taking-me-seriously attitude.
Pocket Full of Rye
Movie alcoholics carry tiny pocket flasks holding only enough booze to make them crave more. Though the flask doesn't contain enough booze to satisfy the drunk, he always offers an offended sober person a drink.
The remarkable ability of a stationary surveillance camera or news camera operated by a lone cameraman to film or video an incident from several different angles and distances all at once. When played back, the resulting film or videotape exactly duplicates the original point-of-view of the audience, right down to the sequence of the montage. See Enemy of the State, etc.
Gun Disposal Rule
The character pulls the trigger, but the gun only clicks, because its empty. So, the character throws it away. Obviously, it will never be needed again.
Last Cell Syndrome
Whenever a character must visit someone in jail, the jailed characters cell is always the last one on the cell block, so the visitor must slowly pass by every other cell in terror.
All bikini-oriented movies, including swimsuit videos, are required by California law to have at least one scene where the top is removed for comic effect. Bonus points if done by a dog.
George Carlin's Toilet-Head Syndrome
"Have you noticed that in the movies a popular thing to do is stick someones head in the toilet and flush the toilet repeatedly? Where did that come from? You never saw Spencer Tracy stick Henry Fonda's head in the toilet. Maybe Katharine Hepburn's, but not Fonda's." -- George Carlin, from Napalm and Silly-Putty.
Cooperative Shooter Rule
No matter what kind of cover the hero hides behind, it will stop enemy bullets. In Beverly Hills Cop 3, Eddie Murphy uses a park bench for cover, and the bad guys to shoot all the slats and none of the gaps.
More Time To Die
When an unimportant stooge of the bad guy is shot, he will fall over and die immediately. But when the main villain is shot, he will remain standing, slowly looking down at the growing blood stain on his chest (see Pirates of the Caribbean).
Grim Reaper's Fertility Clinic
The chances of a heroine conceiving a child with the hero from a one-night stand skyrocket if the hero dies later in the film (The Fly, Terminator, Cold Mountain).
(See Movie Clichés Of The Day, Vol 1)