Peregrine
Sprague
Wolfgang
Huckleberry
Harlan
Hamish
Hiram
Julius
Thelonious
Richard.
Anglo-Saxon roots. It remains the best boys’ name ever. And it’s not very common anymore.
Richard has been ruined (for me at least) by Dick Nixon & the portrayal of Coeur de Leon in The Lion in Winter.
Amos
Linus
Magnus
Ulysses
I second Amos. Ataraxy beat me to it! I’ve always liked that one.
Beowulf of the Geats
Actually, if you were to consider Irish names, I put Cahal into the fray. (Usual spelling Cathal, but it’s pronounced more like Cahal). I’d heard it before, but a recent episode of Grand Designs reminded me of it.
Declan is a lovely name, but very popular in Britain and Ireland.
Roman
Callum is one of my favorite boy names lately, and only partially because of Callum Keith Rennie. It also goes really well with Declan, which has already been suggested.
According to the NameVoyager (which is super fun to play with; it graphs the popularity of any name that’s ever been in the US top 1000 since about 1880) Callum and Declan both have risen in popularity in the US in the past few years- Declan is the more popular of the two.
Joslyn
Beverly
Hilary
Shirley
Waverly
Anne (As I have found out from this thread.)
Were once boy names. There are a few others that escape me
You could go ultra obscure and name him Hilarion. I have a female cousin named Hilarian. It is actually a very lovely name. I’m pretty sure she doesn’t ever have to tell anyone her last name as she is the only one within 3000 miles, if not the entire continent.
Dashiell was my first choice if my daughter had been a boy. However, we decided that we couldn’t use it for my son, because we ended up naming my daughter Dorothy. I didn’t want to condemn my kids to become Dot and Dash. (Although I do think that those would be great names for a kids’ book series - Dot and Dash Morse, the mystery twins.)
Well, a few I can think of…
Izentefsi (Izen rhymes with “mizzen”) Izen-tef-see
Yehtgeisht (Yet-guysht)
Boewobtawnt (Boe rhymes with toe) Boe-wob-tawnt
Tracey is another one. In fact Ice-T who plays a tough macho detective in Law and Order SVU has the first name of Tracey.
My son’s name is Raphael.
Based on my audience, I’ve been known to claim that he was named after the angel, the painter or the Ninja Turtle (in fact, he was named after his grandfather).
Oooh, yes!
Tracey and Stacey.
His grandfather was a ninja turtle?!!!
Just remembered another boy-now-girl name: Florenz. ( My grandfather’s middle name and my middle name, except with the ‘ce’ ending.
Francis ( boy) Frances ( girl)
Aaron
Although I have an ulterior motive for suggesting it! 
I caution against names that seem to be the other gender. I went through school with a boy named for his father, Theada. On the first day of school every year, the teacher asked the same question. “Theada, where is she?”
From about the 4th grade, on through high school, kids love to make jokes out of other kids’ names. When you have a short list, think about unfortunate mocking the name might invite.
A distinguished name is a very cool thing, and maybe always having to spell it out is a small price to pay. How far should you push the envelope? Maybe Ethelred and Constantine are over the edge.
How long is your last name? Federico Chesterton Winklehurst is hard to squeeze into a blank on some forms. If your last name is Bax, go ahead and give him a long name.
If you have a very common surname, for Heaven’s sake give him an unusual first name. Our former mayor gets calls from collection agencies, because another Kevin Smith is a no-goodnik who’s always in trouble. Another guy I know spent the night in the pokey because the other David E. Smith on the Air Force base was AWOL.
If you name your baby after a celebrity, it might be great. Or, the star might be arrested for beating up his girlfriend, or worse.
If you’re going to just make up names, why not make up ones that will be easy to pronounce?
I really like the name Victor.