Basic Trope: Someone accuses someone else of rape, even though that person is beyond a reasonable doubt not guilty.
Straight: Bob is accused of raping Alice, but he didn't.
Exaggerated: Bob was out of the country at the time of the alleged rape.
Downplayed: Bob is accused of having drugged Alice and had sex with her. He did have sex with the drugged Alice, but he wasn't the one who drugged her, and he only had sex with her because he didn't realize at the time that she was drugged.
Alice couldn't see her attacker's face, and misidentified Bob.
Gender Inverted: Bob accuses Alice of raping him, even though she didn't do that.
Bob is convicted of rape, and there is evidence.
It is quickly shown that Bob is innocent, or at least that there is insufficient evidence to prove guilt.
The defense puts Alice's credibility or sexual history on trial, in an attempt to paint Alice's testimony as unreliable.
Bob did actually rape Alice, but it happened so long ago that the statute of limitations on charges has long since passed. Unfortunately for Alice, she waited too long to press charges, out of fear or embarrassment.
The rape trial happened way back in The Seventies, before DNA evidence was really in use; Bob is cleared by DNA evidence in The Nineties and released from Prison.
Or Alice worries that no one would believe her (even if it was a case of date rape), and she doesn't press charges against Bob.
Discussed: "So, I hear Alice is accusing Bob of rape..."
Conversed: "That doesn't sound like Bob; I think there's more to this story."
Bob is quickly found innocent, but his reputation is still ruined. Alice's credibility is destroyed by having made the accusation. Meanwhile, the rapist gets away scot-free and continues to attack other women.