Well, you Americans (Englanders) seem to have a lot of unisex names. And yes. Confusing. Here around I can only think of Misha, Sasha and Vanya. And they are rare and only given by some rusofiles.
There was a guy in the IT section at a temp job I had named Justine. Thing is, he pronounced it Justin, but insisted on spelling it Justine. I just shrugged.
Maybe you can claim it was just a typo instead. 
I currently work with a guy named Courtney. First male by that name I’ve ever met or heard of, though I’m sure there are plenty.
I (also in the UK) have long harboured the “-say, male; -sey, female” notion: but indeed, as per various material in this thread, said notion seems not to hold water. To the best of my knowledge, the only male with the name (either spelling) whom I’ve ever met first-hand, is my niece’s boyfriend – he’s 21 or 22 – his name is the “say” variant. (Though in fact, everyone calls him not by his given name, but by a nickname not related in any conceivable way, to it.)
I recall only ever having met one male Ashley – who came from an Indian Christian family, of all things. (And he was a jerk; but that is of course completely by the way !)
A name which is to my knowledge almost exclusively female, but not quite 100% so, is Evelyn. The best-known male Evelyn would seem to be the British author Evelyn Waugh, fl. earlier part of 20th century. One might speculate on whether Mr. Waugh’s notoriously spiky and unpleasant personality owed anything to resentment at some level, over his being saddled with a first name which some might regard as effeminate…
I have had the unfortunate situation where I looked up a picture of the person and still was uncertain.
Another odd one is Shirley. Notably for a man, Shirley Povich, sportswriter and father of Maury Povich, the paternity test guy. For a woman, Shirley Temple, famed child actress and diplomat. Mr. Povich ended up being listed inWho’s Who of American Women in 1958.
Waugh was also married to a woman named Evelyn… That name used to be more unisex, but now is almost exclusively female (well, old lady).
Surely you can’t be serious!
For unknown reasons, ‘Evelyn’ has experienced a dramatic comeback in the US, and was in the top 20 for baby names last year.
I also remember when ‘Sarah’ and ‘Emma’ were old lady names, though. But I don’t see Bertha, Agnes, or Ethel coming back anytime soon.
I know that Lindsay can be a unisex name but I would have tripped up, too. And I did not think there was a gender difference with the e or a.
Obama’s mother’s name is Stanley Ann Dunham. She used the name Stanley all the way up through high school! Damn.
My girl dog came from the rescue with the name “Morgan” and I kept it. When people hear that name they either think “Morgan Freeman” or “Morgan Fairchild” and assign her gender based on that, I think. But since I’ve been more aware of the name in the past 2 years (since I got Morgan) I have seen it exclusively ascribed to female people.
Dana is another one. I’ve met two males named Dana and only one female.
I love that graph, thanks for linking to it…I’d lost track of it. I like putting in names and seeing where they peak. Eulalie, for instances, hasn’t been around since the turn of the last century. You don’t run into a lot of Maurices anymore (funny enough, that was popular as a girl’s name in the 1910s). I did know an older couple who named their son Vernon.
Caleb was around for a bit in the 1880s, then disappeared, then came back with a vengeance in the 90s.
I used to work with a Russian couple, both of whom were named Sasha. 
My father knew a man named David Smith, and he was determined to give his son a distinctive name. His pick? Courtney.
A male character on Angel was named Lindsey. And before the character appeared on Buffy the Vampire Slayer, I would’ve thought of “Angel” as a female name.
There’s a mystery novel in which the fact that Evelyn is both a man’s and a woman’s name is important. Mrs. McGinty’s Dead, by Agatha Christie.
I can’t believe the OP would look up “Jake” and NOT look up “Lindsay”.
Believe it. As I said, I’ve actually known female Jakes.
My gf has a horse named Jake. Although a male, he’s castrated.
I know a female Shawn (spelled that way), but it’s certainly a male name, in my mind. Lynn can go either way.
The one I’m now hearing that throws me off is Peyton/Payton. When I hear it, I immediately think male, because of Peyton Manning. But I’ve heard of several new baby girls named Payton (at least I think it’s spelled that way). Still not used to it as a female name.
I’m an author and playwright. In my children’s plays, I often give characters one of the above-mentioned names to make it easier to cast, since any kid can play the part. For one of my plays, my editor asked if the characters Chris, Jordan, and Sam were brothers. I said they were siblings, for that reason. She approved.