Basic Trope: One person kisses and/or has sex with someone who's unconscious.
Straight: Alice is lying in a coma at Troperville General Hospital. Her boyfriend, Bob, comes to visit her, and decides she looks so beautiful that he can't help himself, and has sex with Alice. (Which may or may not appear in her coma dream and/or wake her up.)
Alice is dead, and not in a hospital but in a morgue or in a casket.
Every male doctor or nurse at the hospital has his way with comatose Alice. Maybe even a few female doctors/nurses as well.
Bob tries to get Alice pregnant. In keeping with the Law of Inverse Fertility, he succeeds, and Alice gives birth without even realizing it.
Alice wakes up while Bob is inside of her. Instead of feeling frightened or upset, she's happy, and then continues to have sex with him.
Downplayed: Bob gives Alice a kiss.
Alice has Virgin Power, and Bob is a villain; it's an excellent opportunity to strip her of that power.
Bob is trying to wake Alice up by "reminding" her of something she really enjoyed with him.
Exploited: Bob is hoping that the sensations of sex will wake up Alice.
Bob feels that this is unethical (and that sex with someone who can't respond or give any feedback would be empty and unfulfilling anyway) and decides to just wait patiently (or not-so-patiently) until Alice wakes up.