The ultimate in death=defying
Resurrect The Flash!!!!!
By 1985, writers of The Flash comics had run out of ideas for the character. "Running really fast" didn't seem much of a super-power, and Flash villains (they felt) were underpowered in order allow the Flash to beat them. Writers instead turned the focus on the character Barry Allen -- putting him through a soap-opera wringer issue after issue after issue. It become a huge joke. Barry was weeping and crying over some new personal tragedy in almost every issue. It even spilled over into Justice League of America and other comics.
DC Comics rebooted its comic book universe in 1985's "Crisis on Infinite Earths". In this cross-over, a multidimensional being known as the Anti-Monitor attempts to wipe out reality using an anti-matter cannon. The Flash saves the day by uniting all heroes by exposing them to the Pscyho Pirate, and then runs so fast that he can out-pace a quantum trigger. He prevents the anti-matter cannon from firing, although the eventual explosion merges all the dimensions into a single one. Flash himself has moved so fast that he apparently dies.
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In 1988, Secret Origins #2 revealed that Barry Allen turned into a lightning bolt, traveled back in time, and became the lightning bolt that gave him his powers in the first place.
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In 1994, problems with the reboot were attempted with the "Zero Hour" cross-over. This was only partially successful.
In October 2001, DC Comics released Deadman: Dead Again, a five-issue weekly comic. Deadman goes into the afterlife, only to see Barry Allen and other dead superheroes in a kind of heaven.
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Between 2001 and 2005, a time-traveling Barry Allen appears in The Flash comics to help convince The Spectre to erase all public knowlege of the secret identity of Barry Allen and Wally West. Barry also stops Zoom (Hunter Zolomon) and his ally Reverse Flash (Eobard Thawne) from torturing Flash (Wally West) by forcing him to relive the death of his twin children over and over. Barry not only captures Reverse Flash but breaks his neck -- killing him -- before returning to his own time.
In fact, as would be much later revealed in Flash: The Fastest Man Alive #6 (January 2007), it is revealed that this wasn't a time-traveling Barry Allen. Somehow, the Speed Force -- the heaven into which all speedsters pass -- disgorged Barry and a bunch of other speedsters (Max Mercury, Wally West, and Johnny Quick) into Keystone City on an Earth in another dimension. They live there quietly with that dimension's Jay Garrick for four years. (How this alternate dimension can exist prior to the restoration of the Multiverse is not explained.)
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In 2005, DC Comics rebooted its comic book universe yet again with the "Infinite Crisis" cross-over event. The Superboy from the Prime universe begins unraveling the universe by "pounding on the walls of reality". (**snicker** ***guffaw***) Barry, Wally West, Bart Allen, Johnny Quick, and Max Mercury all emerge -- from what appears to be the Speed Force -- to seize Superboy Prime and hold him prisoner. Prime escapes. Bart Allen agrees to absorb the entire Speed Force and restore the Multiverse to prevent Prime from returning once he's recaptured. (Why Barry doesn't do this is not explained. He remains in the Speed Force heaven.)
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In 2008, DC Comics rebooted its comic book universe YET AGAIN!!!!!!!!!!!!!!! in "Final Crisis". (It would not be the final one.) In DC Universe #0 (June 2008), the story is narrated by Barry Allen as an unseen narrator. The narrator seems to remember interacting with Superman, Batman, Green Lantern, and more, and as the story progresses he begins to remember more and realize who he is.
In Final Crisis #2 (August 2008), Barry Allen returns as the Flash -- completely unexplained. The Source has killed of all the New Gods except for Darkseid, Black Racer, and Libra, and merged New Genesis and Apokolips into a new Fifth World. A badly wounded Darkseid lands on Earth, but is now in possession of the Anti-Life Equation. He swiftly takes over the minds of nearly the entire population. Barry leads the Black Racer (the god-slayer under the control of The Source) through time and space, eventually tricking him into ramming into Darkseid. Batman then fires a "radion bullet" into the wounded god, killing him. Superman uses the Miracle Machine from the 31st Century to remake the universe as it was before Darkseid's destructive rein -- although, he remembers it a bit more fondly (with lots of dead superheroes restored to life).
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In 2009, the six-issue miniseries The Flash: Rebirth attempts to explain Barry's resurrection. Wonder Woman explains Barry's two-decade absence by claiming he was in a federal witness protection program. In this series, Barry's mother is murdered when he was a child and his father was imprisoned for the crime. (This is the basis for The Flash TV series.) Barry captures the evil speedster Savitar, but Savitar shockingly dies when he touches him. Barry's existence causes convulsions, pain, and lightning strikes on other Flashes, so he flees back into the Speed Force.
Reverse Flash (Thawne) is there, too: He reveals that just before time-traveling Barry killed him, he captured some of Barry's consciousness and essence and drew it into the Speed Force. (How? And how did he know these events were going to happen??) Thawne reveals that he created a new kind of "contaminated" "negative Speed Force" to infect heroic speedsters. It was Thawne who released Barry during "Final Crisis". (HOW???) He reanimated him with the intent to allow him to infect and kill other speedsters.
Wally enters the Speed Force to retrieve Barry. Barry, Wally, Jay, Max, and Bart -- plus Jesse Chambers and Iris West-Park -- battle Thawne. Thawne reveals that he murdered Barry's mother and now intends to kill Iris West prior to her marriage to Barry Allen. Barry chases Thawne. As he passes the accident that creates The Flash, Barry turns into a lightning bolt and causes himself to gain super powers. Barry and Wally reach Thawne in time to prevent him from killing Iris. As the two Flashes return to the present, they see that the Justice League, the Justice Society, and The Outsiders have built a device to imprison Thawne. When Thawne is tosses into the device, the negative Speed Force leaves Barry.
There you have it: A completely unexplained resurrection, which the writers hope you don't notice in the cacophany of events.