The Hangover Part III: A group of friends go out to make sure the responsible for them not remembering things before stops causing them harm. It doesn't work, and you see them getting harmed as much as possible.
Happy Feet: Several layers of social commentary, wrapped in a 'first contact' subtext, taped with religious and mythic connotations, and directed by George Miller, to boot. Oh, and there's tap-dancing. In Antarctica.
Harry Potter and the Deathly Hallows, Part Two: The boy and his friends rob a bank and nearly destroy his school.
The Haunted Mansion: A workaholic and his kids try to stop a creepy butler from making the workaholic's wife marry a ghost. It's based on a theme park ride.
Heat: Two workaholics find themselves in direct competition as each aims to completely screw up the other's plans, as all the while their personal lives implode spectacularly. The highlight of the movie is a scene in which the two meet for the first time, have a friendly coffee and pleasantly and calmly discuss why exactly they're trying to screw each other over.
Heathers: A popular girl falls for a bad boy as they plan to blow up their school. Hijinks ensue.
Alternatively: Three kids turn into sea creatures because an Absent-Minded Professor is worried about the environment. Soon, they discover that the antidote that was supposed to make them human again gave some fish intelligence. Oh yeah, and Alan Rickman's in it.
High Fidelity: A self-absorbed, broke music store owner is dumped by his lawyer girlfriend, and is bitter about it. Gets over it by hanging out with his employees and sleeping with one of the Cosby children. Later goes into business with teenagers who once tried to rob him.
High Noon: We have to watch Gary Cooper's every move for over an hour. The rest of the town tries to get him to just go away. Most people seem dissatisfied with his choices, including himself. At one point there's a heated debate in which everyone decides not to do anything.
How to Marry a Millionaire: Three popular actresses plot a get-rich-quick scheme by vainly chasing men around New York City. A TV series, which is actually worse than this, is known to exist, but only because the girl who replaced the most popular of three said actresses is a genie.
The Howling: Woman is romantically pursued by supernatural stalker named Edward. Based on the popular novel of the same name.