Aixa

Ajax was the strong and courageous Greek hero featured in Homer's "Iliad," known as Ajax the Great. But it's also the name of a foaming cleanser, and if you find that reference too strong, you might try the shortened Jax instead.

Ajax

Alixe

Putting the emphasis on the "elle" softens a name that seems at once futuristic and medieval.

Axelle

Macho to the max.  But with the rise of x as a fashionable letter anywhere it appears in a name, ala Jaxson or Maxon, we may be hearing more of Axton.

Axton

Anixe

Astianax

Ayax

J.K. Rowling is a modern master of naming who brought a whole constellation of ancient and celestial names to modern parents. Bellatrix, of one of the stars of Orion, combines fashionable names Bella and Beatrix to make a convivial and original name. The down side: the Harry Potter character Bellatrix, played by Helena Bonham Carter, is a character so evil she's called a Death Eater, killing one beloved character and being murdered by another. And the name Bellatrix is so closely associated with that character that it might be challenging to sidestep the association.

Bellatrix

A playful and whimsical choice for a child that works as a given name or a nickname (perhaps for Beatrix).
 
American model Binx Walton (born Leona) was nicknamed by her brothers after the Star Wars character Jar Jar Binks.

Binx

French form of Callistus or Callixtus, borne by several popes and saints.

Calixte

Calixto is known in Spain as the name of three popes, one of whom was the martyr, Callixtus I, regarded as a saint. Calixto has a lot of energy and futuristic spirit, thanks in part to the attention-grabbing 'x.' He is the main character in the Spanish classic, Fernando de Rojas's Tragicomedy of Calixto and Melibea.

Calixto

Callixte

Swashbuckling name worthy of a hero in a romance novel. Deveraux or Devereaux is drawn from the River Eure in France. Mick Jagger has a son named Deveraux.

Deveraux

Devereaux is familiar to many English speakers as a surname but not as a first. It's a habitational name related to the River Eure in France. Mick Jagger has a son with this name in a different spelling, Deveraux.

Devereaux

Dominix

Exton

Fox is one animal name backed by a longish tradition, and then popularized via the lead character Fox Mulder on X Files. Fox is simple, sleek, and a little bit wild, and could make an interesting middle name.
 It was reported that the TV character's first name was not a tribute to the Fox network which aired The X-Files, as often assumed; show creator Chris Carter said he had a childhood friend named Fox. Fox was one of the fastest-rising boys' names of 2016, perhaps because of the popularity of the X-Files revival.

Félix

Fénix

Galaxy

Knox is an old Scottish surname that Brad Pitt (whose great-great-grandfather was named Hal Knox Hillhouse) and Angelina Jolie took out of the back cupboard, dusted off, and elevated to coolness--to the point where it entered the <a href="https://nameberry.com/popular-names">popular baby names</a> list in 2009. Knox now ranks among the most influential <a href="https://nameberry.com/fameberry">celebrity baby names</a>.
 With Knox, the Jolie-Pitts established their own tradition: instead of their sons bearing the same first inital, they share the final letter 'x'--Maddox, Pax and Knox-- as well as a final 'n' for their <a href="https://nameberry.com/list/673/middle-names">middle names</a>. It's celebrity shine has made the formerly obscure Knox one of the most popular <a href="https://nameberry.com/list/473/scottish-names-for-boys">Scottish names for boys</a>. 
 The surname Knox dates back at least to the thirteenth century, and John Knox was the priest who brought about the Reformation in Scotland.

Knox

Lennox is an aristocratic and powerful Scottish surname name made truly special by that final x. The worldwide fame of British boxer--World and Olympic champion--Lennox Claudius Lewis brought the name into the spotlight as a first name, while as a last it's tied to Eurythmics singer Annie L.
 The Thane of Lennox appears in Macbeth, Mary Lennox is in The Secret Garden and there are two Agatha Christie characters with the name.
 Lenox is another accepted spelling.

Lennox

Lennox is one of the new breed of surname names on the rise as a <a href="https://nameberry.com/list/472/scottish-names-for-girls">Scottish name for girls</a> as well as boys. The final x makes the name a bit masculine a la Max and Felix, but female inspirations include Eurythmics' Annie Lennox, Mary Lennox in The Secret Garden, and Lennox Scanlon in sitcom Melissa & Joey.

Lexus, an automotive newcomer, has recently entered the Top 1000 -- more because of its association, we fear, with the status symbol car than its relation to the name Alexis. If you love this name, do your child a favor and make it Alexis or at least spell it Lexis.

Lexus

Luxor is just waiting to be discovered as a baby name. It has a lot going for it — an easy and fashionable nickname (hello, Lux!), unisex appeal, and a place name connection. Luxor is the modern-day name for the ancient Egyptian city of Thebes. It was derived from the Arabic term al-ʾuqṣur, referring to palaces or castles.

Luxor

One of the fierce new animal names new to name lists, helped by its strong x-ending.

Lynx

A fresher spin on Jaxon, with built-in cool nickname Nix, and a great way to honor an ancestral Nick. But the association with disgraced former president Richard Nixon remains strong, which might explain why this otherwise bang-on-trend surname name has remained under the radar, peaking at #482 in 2017.

Nixon

In Greek mythology, Nyx was a powerful goddess and the embodiment of the night, but when spoken, its negative meaning can't be ignored. 

Unlike Pearl and Ruby, this is one gem name suited for boys, the final x making it sound strong and virile. Musician Iggy Azalea chose the name Onyx for her son.

Onyx

Onix

Orix

Oryx

Oxsana

Phoenix rolls a lot of cool trends into one: it's a place-name and a bird name, it ends in the oh-so-hip letter x, and as the mythic bird that rose from the ashes, it's a symbol of immortality. 
Phoenix is a fairly evenly-balanced unisex name, though it tilts slightly to the boys' side. Last year, it was given to 1300 baby boys and 1000 baby girls.

It's also got celebrity chops, via the acting family that includes Joaquin and the late River, and as the son of Paris Hilton.

Phoenix

Phoenix is a New Age name symbolizing rebirth and immortality. It's also a place name, a color name, a mythological name, AND an animal name, combining several of today's hottest trends in one appealing package.

Phoenix is also a fairly evenly-balance gender neutral baby names, given last year to about 1000 baby girls and 1300 baby boys. Scary Spice chose Phoenix for her daughter, and Paris Hilton used it for her son.

Pixar

In Greek mythology, the river Styx separates the Earth and the Underworld, named for the goddess who gave it its power. Today Styx is also associated with the 1970s rock band of the same name.

Styx

Xever

vix's list "unique names with x" of 39 great name ideas: Aixa - Xever!