Often, I get the feeling that entire concepts are built around the title first. Here are a few examples:
A Million To Juan a man named Juan inherits a million dollars.
Legally Blonde an over-the-top blonde stereotype goes to law school.
Transamerica a trans woman drives across the United States.
Racing Stripes a zebra becomes a racehorse.
Back To You much-hyped, extremely doomed TV series about a divorced couple anchoring the news together.
Blacula Black remake of Dracula.
White Blacula: The Black Version Black remake of the Hollywood remake of Blacula.
In this spirit, here are a few movie ideas that I would propose:
Your Mileage May Gary a man who cheats to win a marathon goes to ridiculous lengths to prevent himself from getting caught afterwards in order to keep the prize money. But, here's the big twist the audience will never see coming: his name is... Gary!?
Don't Tread On Me a talking Sherman tank named Sherman travels back in time to help win the Revolutionary War for the American colonists. Tanks have treads.
Hope Against Hope two women, both named Hope, are competing against each other in something. I dunno, an election maybe?
The Adventures Of Venus de Milo And Otis Kiddie fare following the exploits of a kitten and a puppy. However, about ten minutes into the film, when the kitten discovers that it is expected to be sent over a waterfall in a cardboard box, it abruptly leaves the set and understandably does not return. The kitten is then replaced with a replica of the famous Venus de Milo sculpture, and the remainder of the film is dedicated to showing us how puppies act in the presence of great art (assuming the dog can't tell it's not the real thing.) I'd pick Russell Brand to narrate.
Robbin' Peter To Pay Paul Mired in financial debt to bandmate Paul Stookey, folk singer Mary Travers sees only one way to escape being sent to debtor's prison: a high-stakes catburglary at the mansion of billionaire friend Peter Yarrow. Can she really pull off such a hairball scheme? Maybe she can, with the help of legendary thief and folk music aficionado Robin Hood, who has traveled forward in time to 1967 to see the trio perform! (This one would require a disclaimer informing the audience that it is a work of fiction.)
Dead Ringer an NBA player's sudden death is good news for a struggling college team, who resurrect him so that he can play for their school as a zombie. But it turns out that dead pro athletes are just as hard to control as the living ones. (If this one isn't already in production, it probably will be by the time you read this.)