Roy: Huh ... I always thought the "revolving door afterlife" was just a metaphor ...
Bureaucratic Deva: Now, you are an adventurer, so that means you're eligible to earn Frequent Dying Miles every time you stay with us...
Balinsky: Oh, Dr. Jackson's gonna die when he sees this!
Dixon: What, again?
— Stargate SG-1, "Heroes"
IMAGINE WHAT SORT OF MESS THE UNIVERSE WOULD BE IN IF WE KEPT SENDING PEOPLE BACK FROM THE DEAD ON FLIMSY PREMISES.
Don't get the wrong idea, though; coming back from the dead isn't a snap. It's a tough narrative trick that requires time travel, a previously unmentioned clone, a cosmic resurrection, an alternate dimensional rebirth, or an inattentive editor with a drinking problem. But it can be done.
Sometimes it seems that in mutant heaven there are no pearly gates, but instead revolving doors.
— Professor X, X-Factor #70
Rachel Summers: Are you sure she (Psylocke,) was really dead to begin with?
Rachel: Don't get mad, I'm only asking. I mean, it's just that death and the X-Men seem to have this... problematic relationship.
Bishop: She was stabbed by a broadsword. And then, because of the circumstances, she was autopsied. That dead enough for you?
Rachel: I suppose she could be a clone.
Psylocke: Ex-scuse me?
Rachel (quietly): Or not.
— Uncanny X-Men v1, #455
She said "I had the strangest dream,
I dreamed I killed you again
Don't make me kill you again,
'Cause I couldn't bear to kill you again."
— They Might Be Giants, "Ondine"
Oh gosh I forgot to honor our fallen heroes. In my line of work everyone just comes back in a couple months.
Starfield: Blurr is about as unambiguously dead as a Transformer can be, IMO.
KrytenKoro: According to Wyatt, in Animated grey=dead, and only grey=dead. Blurr is still alive.
Starfield: Like I said, as unambiguously dead as a Transformer can be. There's always a chance. (Even when they are gray.)
— Two Editors on Transformers Wiki
"Oh dear. I seem to have died. This is very inconvenient."
— Jacob Deegan, Dominic Deegan
Jerry the Immortal: "Dying is going to put me out of commission for a few weeks."
Susan: "Dying is usually inconvenient."
"Death has lost its meaning. The doorway between life and death has been cracked open for years. Ever since Superman came back to us. And then Oliver Queen, Hal Jordan, Jason Todd."
— Raven, Teen Titans #30
Sigma: "Aah! Teddy bears thrown at me! My only weakness! ..For now..." *Falls over dead*
* Less than two seconds later*
Sigma: "Muahahaha! I'm back to get my revenge! *Evil Laugh* So... what was the time?"
Zero: "Hmm... Sorry, not a new record."
— Sigma and Zero, Mega Man X: The Maverick Breakdown
"We're just going to kill you, and then you'll be fine!"
— Agatha, Girl Genius
Doctor Sun: I will be the judge of that. Where is he? [Vole holds the man's severed head in his hand] Yes. Well. Tricky. But I've seen worse. Let's get him prepped.
Blutarch Mann: "All I ask is that you-" *Blutarch dies mid-sentence*
* Eerie silence*
Engineer: "Uh... Sir? Is he alright?"
Blutarch's secretary: "Give him a moment, dear. He's just dead."
* Life support machine shocks Blutarch back to life*
The coward dies a thousand deaths; the brave man dies but once; the Warrior Princess dies about once a season, to keep in practice.
— Kevin Wald
Itís an interesting thing, death in Science Fiction. With technology so advanced, if the author wants to make sure the reader wonít think the character will be brought back to life, the author canít just shoot or dismember the character, the character really needs to be disintegrated.
We wonít even TALK about cloning.
Professor Mezzasalma: "...Mittlemind there has a pulse cannon built-in. It killed him, of course, but her gun did blow up."
Moloch von Zinzer: "That ... that was very brave."
Professor Mezzasalma: "Oh, please. Don't start. He'll be smug enough as it is."
"Moving for me is a multi-annual tradition, much like killing John has become."
"Wounds are becoming troublesome. At 8, they may become fatal. Which would be inconvenient."
— Fallen London, description of the "Wounds" trait
Fry: "Take that Grim Reaper!"
Bender:(under his breath) "Stupid, ineffective Reaper!"
— Jurassic Bark, When cloning Fry's dead dog
"Oh no you don't! We know how it goes: you take the body, then he's back in a week!"
"You know, if everyone The Punisher killed turns out to be no more dead than anyone else who "dies" in Marvel Comics, he's going to be in BIG trouble one of these days."
— Marvel Year In Review 1993
"But I stopped reading Ultra-Powerful Guy the ninth or tenth time he died and came back."
— Nermal, Garfield #1
King Kai: Goku could not escape the explosion. Namek is gone...and so is he.
Yamcha: No...Goku, no! (emotional music) Noooooooo! (falls to his knees and cries)
Tien: (music cuts off) Why do you care? Why do any of you care? Are you forgetting the whole reason that they went to Namek in the first place? Now we have two sets of Dragon Balls.
Yamcha: Well, yeah, but...you make it sound like death has no consequence.
Tien: It really doesn't. We're literally waiting to go back. Hell, this is Chaotzu's second time.
Chaotzu: Next time I get a free sundae!
King Kai: Huh.
Where's Ra's? If he's dead again, I need you to wake him up.
— Batman, Batman Arkham City
Murder as warning
The assignment is simple enough. A journalist has said too much, and someone wealthy would like him to be murdered. Heíll get better, obviously, but it will serve as a warning.'
— Opportunity card in Fallen London
X: Okay, I think we're safe now, Ran. Ran?
(Ran teleports in)
X: Ran, what happened?!
Ran: I didn't make it. Twelve freaking times!
You boys die more than anybody I ever met.
— Ash, Supernatural
Old Kai: I'll give you the life that's left inside of me, that way you can make your way to Earth. (Old Kai sacrifices himself and dies)
Goku: (Goku's Halo fades away) Thank you, I promise I won't let this go to waste.
Old Kai: (wakes up with a Halo) THEN HURRY UP!
Old Kai: WHAT are you doing!? You're standing there looking like fools when you should be saving the universe!
— DBZ 
"Ha ha! I died again!"
— Lynne, Ghost Trick
"Remember when Scully was having a baby despite having no ova? Or when Mulder died? Or that other time Mulder died? Or that other, other time Mulder died?"