In Dan Abnett's Gaunt's Ghosts novel Ghostmaker, Dorden has authority to go into the ship's supplies, and yells at someone trying to check up on him: he is trying to get medical supplies for a soldier in critical condition.
In Sandy Mitchell's Cain's Last Stand, Ciaphas Cain, hearing Magos Tayber wants to talk to him, knows it's a matter of life and death because she didn't vox him.
In Terry Pratchett's Mort, Mort wakes up Ysabelle in the middle of the night and demands she come help him, urging that it's a matter of life and death. (Death had vanished.)
In Angie Sage's Septimus Heap book Flyte, Jenna insists on a message being sent because it's a matter of life and death. Later, when Marcia and Aunt Zelda quarrels, it's on the grounds that it's a matter of life and death.
In Poul Anderson's "Marque and Reprisal", a spokesman speaks of how the issues before them are of life and death.
In Sarah A. Hoyt's Darkship Renegades, Thena reflects on how treating the mental ill started only after it became feasible; before, when they could threaten the existence of the tribe, they were probably killed.
Goodbye, Mickey Mouse by Len Deighton. A married woman rings the US airbase demanding that the American pilot she had an affair with get in contact with her immediately. On being asked if this is a matter of life and death, she shrieks that it is and hangs up. When the pilot goes round to her house, he finds that her husband who's returned from fighting in Burma forced her to make the call at gunpoint as he's planning a Murder Suicide of all three parties.
Devinoni Ral: Yes - protection. Your protection, your captain, your crew, your...edge. Yes. Now, it's a matter of life and death when you take the advantage; me...I deal in property - exchanges. Nobody gets hurt. So you tell me - which one of us would you say has more of a problem with ethics?
Narrator: [opening narration]Twelve o'clock noon. An ordinary scene, an ordinary city. Lunchtime for thousands of ordinary people. To most of them, this hour will be a rest, a pleasant break in the day's routine. To most, but not all. To Edward Hall, time is an enemy, and the hour to come is a matter of life and death.
Spoofed in Get Smart. Maxwell Smart is trapped in a phone booth that's flooding with water. He tries to ring Control for help, but finds he's run out of quarters.
Smart: Operator, this is a matter of life and death!
Operator: That's what they all say.
On Arrested Development, Lucille Bluth consistently refers to one of these in text messages as "a matter of land" (she means "l" and "d"). People mostly wind up wondering what land has to do with anything.
Walter Sobchak: I'm saying, I see what you're getting at, Dude, he kept the money. My point is, here we are, it's shabbas, the sabbath, which I'm allowed to break only if it's a matter of life or death...
A good line from The Penguins of Madagascar comes from when Julian busts into the penguins home while they're busy. "This better be a matter of life or death, Ringtail. Because if not, then we can arrange those stakes!"