Are there any great unsolved Batman mysteries?

[BatmanBeyond28]

I can't think of any.

Maybe I shouldn't be surprised if the greatest detective in the world leaves no cases unsolved but I think it kinda sad that a character so steeped in mysteries doesn't have any mysteries lingering for fans to debate for ages/try to solve.

[Myskin]

There are a couple of them.
1- Who was the Holiday Killer in The Long Halloween? Personally speaking I had no doubt (there were two killers, the one who was revealed and he one who is talking at the end of the story... I'll avoid spoilers, just in case). But Loeb added a couple of lines to the ending which really confused me. Basically, without those two lines the whole story would be resolved. Instead, it is a bit of a mess. But that's typical with Loeb. This doesn't change the fact that the Long Halloween is one of my favorite stories ever.

2- Who was the Skeleton? To be fair, the Skeleton story was never really written. Brian K. Vaughan created the character for a brief intro in a Secret Files issue, but no story followed and to this day he never said who the Skeleton was supposed to be.

3- Who was the Red Hood? Not the one in regular continuity, I mean the character created by Dan Slott for his Batman Adventures series. The series was cancelled before delving into the mystery.

[taylortexas]

I may be remembering this incorrectly, but didn't Snyder's Black Mirror story during his time on Detective Comics end on a cliffhanger that was never resolved? Dick (as Batman) had a USB drive that contained some sort of monumental revelation but it's never revealed. Was that just leading to a pre-FP version of Court of Owls and so they waited to use that in the New 52?

And I should say that I actually really like the idea of a great unsolved mystery that plagues Batman (and us, for that matter). It's that cold case that every single fictitious detective apparently has. Not even the world's greatest detective should be exempt from that trope! I suppose this could have simply been his parent's murder until Joe Chill happened.

[Green Goblin of Sector 2814]

Does the Joker's true identity count?

[BatmanBeyond28]

Yes, but I think they should have more than one great mystery for readers. They should drop mysteries all the time. Maybe some Batman should know of and can't solve and some could be stuff the readers see and that Batman doesn't even know about (to protect his reputation). The writer and the artist could leave clues to actually solving it in the writing/art but never explicitly give us the answer.

[Aahz]

Was it ever really revealed what was the deal with the White Rabbit?