Edit: I remember and type way too slow, but I’m leaving this here anyway. I still think it’s worth seeing, too.
The Usual Suspects: Verbal Kint is an awkward small-time crook with cerebral palsy, being questioned by Detective Kujan about what happened on a boat that led to many deaths and the boat being set afire. The only other known survivor is in bad condition in the hospital. Kint tells the story in flashbacks, alternating with interrogation.
Weeks prior, a bunch of the “usual suspects” (cf the movie box/poster image) get hauled in for a lineup; this includes Kint. Afterwards, one of them proposes a big hit on some corrupt cops. They fence the loot, and get a jewel heist offer from the fence.  They end up with heroin instead. The fence points them at who told him about the job, who ends up being Mr. Kobayashi, a lawyer for the mysterious Keyser Soze.
Soze, they are told by one of the others in their group, is a near-mythical Hungarian mobster who is utterly ruthless. When rivals kidnapped his wife and kids and confronted him, threatening to kill them, he killed his own family himself, and then all but one of his enemies so that the survivor could tell the tale. Almost no one even knows what he looks like. He works through intermediaries.
Kobayashi says Soze is pissed about the heist. One tries to run and is killed. The others grab Kobayashi. He pulls out dossiers on each of them about their loved ones and private lives, threatening their loved ones and blackmailing them all into attacking a rival’s boat and destroying the huge supply of cocaine on board. They are welcome to the cash if they stick around to confront the buyers.
We’ve come to the story at the start of the film: one of the characters named Keaton, who was trying to go straight, tells Kint to hang back, and split some of the money with Keaton’s girlfriend if things go bad. Two of them search the boat and find no cocaine. One goes after the vehicle with the cash and is killed. One of the foreign mobsters is killed by someone unseen. The others in the group are killed one by one.
The detective tells Kint that one of the dead mobsters his group ran into was a man claiming he could identify Soze; the other group there (Hungarians) was trying to buy out this guy so they could find Soze and take revenge. Soze had sent this group of small-time criminals to be a distraction so he could have the witness killed. Kujan beats down Kint’s story, trying to get him to admit that this was a setup for Keaton to fake his death (he’d done it before), and Kint breaks down and says it was Keaton’s plan to do a lot of what they did and that no, maybe he didn’t really see Keaton die. Then he clams up; his bail has been posted and he gets to leave.
[spoiler]Kujan looks around the room - he’d borrowed an office from someone else for the questioning - and starts seeing details from Kint’s story: a coffee cup made by the Kobayashi company, names from articles and other things around the room, etc. He realizes it was all made up and runs out of the room. Meanwhile the witness in the hospital had woken up and gave a description of the killer at the docks, repeating Soze’s name over and over. A fax comes through with the artist’s rendering of “Kint.”
“Kint” leaves the police station and his crippled gait and stance straighten up. He gets into a car driven by “Kobayashi,” and they drive away. Kujan runs out of the police station and looks around frantically.
The last line is a flashback to something said by Kint about Soze - “The greatest trick the devil ever pulled was convincing the world he didn’t exist.” And then another line: “And like that, he was gone.”[/spoiler]