No death is permanent in comic books. For decades there was the eternal standard of "No one stays dead except Bucky Barnes", and we see how that turned out.
But sometimes bringing a hero back requires a good bit of imagination. After all, when you kill off a character (sometimes in in some seriously permanent ways like blowing them up), it takes a little creativity to find a way to bring them back. Even comic book readers like a little dose of reality here and there for it all to make sense.
Anyway, here are some of the best returns yet:
When your character is killed by popular vote of the fans, you pretty much figure he's one of those that will be gone forever. Well, that wasn't the case. DC gave everyone a hint of what it might be like for Jason to return in the "Hush" storyline of Batman, and it was enough to get the internet buzz going. Eventually DC brought him back as the Red Hood, and we finally saw potential in the otherwise spoiled character.
The way he came back was about as convoluted as it could possibly be. Superboy Prime beat on the walls of reality/time so hard that it brought Jason back from the dead, though with a lot of memory problems. Talia found him and helped nurse him back to health before sending him back on his way. Eventually, Jason remembered everything and nursed an understandable grudge against Batman that led to some great confrontations.
Jason went from an interesting foil for Batman to a serious contender for the cape and cowl someday. During the Countdown to Infinite Crisis series we saw him even take on the role of Red Robin (though he mysteriously dropped it again after the series was over and Grant Morrison said no). Jason is still a major player in the DC universe, even though he has stepped back from the spotlight a lot since the Countdown series. If it ever comes time to find a replacement for Batman, Jason will be second only to Dick Grayson for the title.
When Earth's greatest Green Lantern turned bad and killed a bunch of folks (including Sinestro), we all knew he was coming back someday. The question just remained a matter of when. DC kept a tight lip on it all and even managed to give us a nod or two that direction during his run as Parallax.
When Parallax died saving the universe in The Final Night, it seemed DC had put a final nail in the coffin of Green Lantern, telling fans to get used to Kyle Rayner because he wasn't going anywhere.
But then the Spectre came along...
Given the chance to make up for the mistakes of his past, Hal became the Spectre and popped up in the DC universe for years. During Identity Crisis, Green Arrow voiced what many readers had questioned for years: "When are you coming back?" Hal's answer? "I'm working on it." It proved the rumors of Hal's return weren't just rumors after all...it was just a matter of "when".
Finally though, the fans got their answer. In a six-part miniseries that stands as one of the best DC has put out in a long time (Green Arrow uses the power ring! How cool is that!), Hal finally returns. DC explained away his crazy time as being corrupted by the Parallax being (and it was the reason he went prematurely gray). Since he's come back, Hal has turned into an incredibly popular character again. Green Lantern comic sales have picked up considerably, and we even got to see the return of the Green Lantern Corps. All in all, DC definitely handled this well.
How do you bring someone back after they've been blown to bits? That's easy to accomplish if your best friend is one of the most powerful figures in the DC universe.
During Hal's last few minutes before sacrificing himself as Parallax in The Final Night, he paid a visit to Oliver Queen's grave to say goodbye...or in this case, to say hello again. The first major indication we had that Hal was truly repentant for what he'd done came in four simple panels with no word balloons. Hal stands alone at the graveside, he glows, and then he's not alone anymore. These panels didn't actually appear in The Final Night (they showed up in a GA comic later), but this is the timeline in which they were supposed to have happened.
We wouldn't actually see Ollie's return until his own comic series picked it up, but this was the actual moment he came back. Since then, Green Arrow has led a full life of fighting bad guys, becoming mayor, and eventually getting married. Not bad for a guy who exploded a few years ago.
Ok, so he wasn't really Captain Marvel, but he didn't know that for a long time. And technically, he had all of Mar-vell's memories, so that makes him the best we're going to get.
There were a lot of things about the Secret Invasion that didn't work, but the way Captain Marvel became such a major player in the storyline was great--especially considering the fact that it wasn't even the real thing! The Skrull replacement process worked too well here, and they found themselves facing the return of their greatest enemy by their own hand. I really wouldn't mind if Marvel brought the real Cap back someday, but I doubt that will happen. His death is iconic, and the hero honestly only became interesting after he died.
Speaking of iconic deaths, this is the one that held top spot for years. This isn't really fair since he never technically died, but was kept in suspended animation for decades, but I'll mention him anyway.
Bucky's death was this huge moment in comic book history that never actually took place until decades later than it supposedly happened. There was never an original issue of Captain America from the 40's that showed this moment. Cap and Bucky just disappeared for a while and were replaced with different guys in the 50's. When the real Cap was brought back in the Avengers comics, we finally learned where he had been for those years and he told what he believed had happened to his partner. Recently it was revealed that the same freezing process that had saved Cap had also saved Bucky--though Bucky was found earlier and not by friendly folks. Instead, they turned him into a killing machine called "Winter Soldier", putting him back in suspended animation for years at a time when he wasn't needed.
Marvel took a huge risk bringing Bucky back, and it turned out to be the best move they could have made. When Captain America was killed after discovering his old partner was still alive, it just made sense to let Bucky fill the suit. He's done a great job of it so far!
There are several more heroes I could mention here, but these were the top ones that came to mind for our first look at comebacks. I'm open to suggestions for a follow-up.