Bullock swung by the Razzies on the eve of her expected triumph at Sunday's Oscars, where she is considered the favorite to win best actress for "The Blind Side."
If she wins Sunday, Bullock will be the first person to win an Oscar and a Razzie over the same weekend.
"I think this is an extraordinary award," said Bullock, who had promised throughout awards season that if she won the Razzie, she would accept it in person. "And I didn't realize that, in Hollywood, all you had to do was say you'd show up, and then you'd get the award. If I'd known that, I would have said I was appearing at the Oscars a long time ago."
"Transformers: Revenge of the Fallen" was picked as last year's worst picture and won two other Razzies: Worst director for Michael Bay, and worst screenplay for Ehren Kruger, Roberto Orci and Alex Kurtzman.
Bay and his team probably will not lose any sleep over it. Though reviled by critics, "Transformers" took in $402.1 million domestically, No. 2 on the 2009 box-office chart behind "Avatar."
Bullock, who also shared the Razzie for worst screen couple with "All About Steve" co-star Bradley Cooper, was the first acting winner to show up at the Razzies since Halle Berry won worst-actress for "Catwoman" five years ago.
As she took the stage, Bullock pulled a little red wagon filled with DVDs of "All About Steve," saying she was giving a copy to everyone in the audience of about 300.
Bullock implied that many Razzie voters had not actually seen the movie but cast ballots for her hoping to get her to show up at the awards. Bullock said if they watched the DVD - "I mean really watch it" - and decided it was not the worst performance of the year after all, then she would come back next year and "give back the Razzie. ... then we'll go drink afterwards."
The worst-actor Razzie went to siblings Kevin, Joe and Nick Jonas for "Jonas Brothers: The 3D Concert Experience."
The Jonas' pal Miley Cyrus, star of "Hannah Montana: The Movie," lost the worst-actress category to Bullock. But her dad, Billy Ray Cyrus, was named worst supporting actor for the big-screen "Hannah Montana."
Sienna Miller received the worst supporting-actress Razzie for the action tale "G.I. Joe."
Will Ferrell's action comedy flop "Land of the Lost" had come in tied with "Transformers" for the Razzies lead with seven nominations, but it was nearly shut out in every category.
Once ballots had been counted from the roughly 650 Razzies voters, "Land of the Lost" was tied for the group's worst remake, rip-off or sequel prize. Razzies founder John Wilson, who always votes last, gave the tie-breaking vote to "Land of the Lost."
"It really did stink and I thought, 'Well, it ought to get something, because it is a very bad movie,'" Wilson said.
Razzie voters also made worst-of-the-decade picks, with John Travolta's science-fiction debacle "Battlefield Earth" winning worst picture.
Among all-time Hollywood dreck, "Battlefield Earth" is "like the 800-pound mongrel gorilla in the room," Wilson said. "It's one of my favorite type of bad movies. It's so bad, it's entertaining, in ways that the people who made it had no idea it would be."
Paris Hilton was chosen as the decade's worst actress for movies such as "The Hottie and the Nottie" and "Repo: The Genetic Opera." Eddie Murphy, a 2009 Razzie nominee for "Imagine That," was named the decade's worst actor for such bombs as "The Adventures of Pluto Nash," "I Spy" and "Meet Dave."
By AP Movie Writer David Germain; AP Writer Mike Cidoni contributed to this report