Lazarus, of course. (Well, he really was dead, but again, he got better.)
Robert E. Lee’s mother was pronounced dead several years before he was born but got better.
Scrooge is shown his grave and lives to tell the tale.
There are several movies (most of them starring Meredith Baxter) about veterans presumed dead who returned home. One is WELCOME HOME starring Kris Kristofferson.
Juliet does the “I’m not dead yet” bit to less than happy results.
Odysseus is presumed dead in The Odyssey.
Millions of people have actually theorized that Elvis is dead, but one day he’ll show them. (You’d think that his daughter marrying Michael Jackson would have called him out, but he’s crafty.)
How about the ending to “Murder by Death” that has the killer revealed to be first Alec Guinness, then Truman Capote, then Nancy Walker (all of whom were murdered in the course of the movie.)
And from Monty Python’s Holy Grail" the “bring out your dead” scene, and Lancelot’s brave patsy who gets an arrow in the gut:
“Brave squire, you shall not have died in vain!”
"I’m not dead, sir Lancelot.’
“Oh…well, you shall not have been mortally wounded in vain.”
“I could recover, sir.”
“Well then, you shall not have been laid low in vain!”
“Actually, I could go with you to storm Swamp Castle!”
“Er, no…just stay here.”
“As you wish.”
Annakin Skywalker was “killed” by his master, “Obi Wan” Kenobi, who was also dead and no relation to Ben according to Uncle Owen. In both cases, it wasn’t so much death as a name change- 10 credits at the local Galactic Courthouse and they were good to go. (And just how powerful could Vader be? All Kenobi did was change his first name then go hide on Vader’s home planet, but let me not hijack.)
The funniest scene in the play/movie A FUNNY THING HAPPENED ON THE WAY TO THE FORUM has to do with a dead virgin who ain’t so dead. (Jack Gilford as Hysterius as the dead virgin is a classic moment in a not very good movie.)
Hester’s husband in THE SCARLET LETTER is presumed dead but shows up. (In the Demi Moore version, which is probably what Hawthorne envisioned but just never got around to writing due to lack of addictions, her ex- becomes a serial killer; it’s one of those “Robert DuVall turned down GODFATHER 3 but he took this?” moments.)
Oedipus, Perseus, and other characters from mythology were “killed” as infants, but the job wasn’t so well done and they showed up 20 years later.