Some famous examples of these are:
"It was the best of times, it was the worst of times." -- Charles Dickens, A Tale of Two Cities.
"It is a well-known fact that a man in possession of a fortune must be in search of a wife." Jane Austen, Pride and Prejudice.
"But it's the truth; even if it didn't happen." -- Ken Kesey, One Flew Over the Cuckoo's Nest.
"Elmer Gantry was drunk." -- Sinclair Lewis, Elmer Gantry.
"One hot August Thursday afternoon, Maddie Faraday reached under the seat of her husband's Cadillac and pulled out a pair of black lace underpants. They weren't hers." -- Jennifer Cruisie, Tell Me Lies.
Grabbers are important partly because of the short attention span of many readers; but also because when people decide to purchase a book, they often do so by reading the book's beginning to see if it's a go or a no-go.
Here are some grabbers from Grabbers R Us: a site for novelists-to-be who can't think if le mot juste to get things going:
"My God, said the Princess, get your hand off my thigh!"
[Offered in response to the suggestion that you are sure to get your reader's attention if you mention the Deity, royalty, or sex.]
"Somehow Kim K. and a kangaroo came in a chrome Volkswagen."
"Elvis is dead, and I don't feel so good, myself."
"Because Millie was tired of sleeping with her pet cat, it meant that she was either going to get a man, or banish kitty to the laundry room."
"Because Mordred knew that the only time he could be on the throne is when he answered nature's call in the morning, he decided to conspire against King Arthur."
"It is an established truth that all politicians wear hats and underwear too large for them."
"Zoltan found himself strangely indifferent to the fact that he metamorphized into a chicken; think of the low cost of feed."
"Karen was relieved that the guy she woke up in bed with was only Thomas."
"Heather saw her mismatched sock draw as a metaphor for her life."
"Cicero blamed his fight with Millicent on the tuna casserole."
"Heather finally lost it after Portia said 'I told you so' for the 143rd time."
"Just what the Archbishop needed as a souvenir for his Rome pilgrimage: A Pope on a Rope to wear in the shower."
"I'm not really completely naked," hinted Françoise coyly on the telephone.
"Roger woke up with a splitting headache and a trophy labeled ' Panama City's Ugliest Butt Contest, Second Place." This caused him to wonder who won."
"An unmistakable sign of shipboard decapitation: A head in the head."
"Ivan Pavlov drooled at the prospect of some further research in this area."
"The Seventeenth Avenue levee broke; but all remained slumbering."
"Billy Bob was blasé after having sex with a cheerleader and he had left his hound dog sleeping under the porch."
"Giacomo, having received news that he was elected Governor, said 'Oh, shit!'"
"He was well-versed in the perversion peculiar to the Cleveland area."
I wish I had stories to follow each of those!