Notable characters who never got a full name (in canon, at least).

[Vandervecken]

The Traveller.
Governor Kodos.
The Albino.
Boothby.

We all know that Boothby's first name is Martin.

Ok. I'm probably a dope for having checked MemAlpha, but... huh?wha'?

Ray or Arnold I'd have gotten...

 

[Captain Rob]

Ever heard of the classic TV show "My Favorite Martian"?

 

[Enterprise1701]

And neither did Captain Braxton nor Lieutenant Ducane in "Relativity". NF: "Double Time" named the latter "Juel Ducane".

No, I named him that in Watching the Clock. I'd be very surprised if Peter David independently chose the same name I did. (I figured that "Ducane" was probably a simplified, futuristic spelling of the French name Duquesne, so I gave him a simplified spelling of "Jules" for his first name.)

Oops. I read that from Memory Alpha.

Gul Evek, one of the only characters ever to appear on all three TNG era TV series, only received the name "Evek" onscreen. The Badlands, Book Two named him "Aman Evek".

 

[Mr. Laser Beam]

I know Braxton's first name has never been revealed, but I personally believe it is Albert.

Meaning, I think Braxton is the same person as...

Spoiler: idea

Al the Bartender from the final episode of Quantum Leap.

 

[Tosk]

Gul Evek, one of the only characters ever to appear on all three TNG era TV series, only received the name "Evek" onscreen. The Badlands, Book Two named him "Aman Evek".

Isn't it funny that pretty much all the characters who appeared on all three 24th Cent shows were one-namers? Evek, Quark, and Q.

Am I missing anyone? There's a few "not quite" ones like Riker, but it was Will Riker in VOY and Tom Riker in DS9. And The Doctor, who was a different EMH in both First Contact and DS9.

 

[Vandervecken]

Ever heard of the classic TV show "My Favorite Martian"?

OHHHHH!!!! Yes, I even saw some when I was a kid. Ok, yep.

 

[Drone]

^While we're on the subject of Danielseses, Crewman/Temporal Agent Daniels from Enterprise never got a full name -- in fact, Daniels probably wasn't his real name anyway.

May I proffer Michelin Man???

 

[Enterprise1701]

Gul Evek, one of the only characters ever to appear on all three TNG era TV series, only received the name "Evek" onscreen. The Badlands, Book Two named him "Aman Evek".

Isn't it funny that pretty much all the characters who appeared on all three 24th Cent shows were one-namers? Evek, Quark, and Q.

Am I missing anyone? There's a few "not quite" ones like Riker, but it was Will Riker in VOY and Tom Riker in DS9. And The Doctor, who was a different EMH in both First Contact and DS9.

Hendorff from "The Apple". Issue #13 of the ongoing IDW series set in the Abramsverse gives him the initials "G. P. Hendorff". Not a full name, but it's a stride in almost exactly 45 years.

Captain Styles from The Search for Spock. I'm not sure which work gave his full name as "Lawrence H. Styles".

The Klingon Ambassador from The Voyage Home and The Undiscovered Country. The novelization of The Undiscovered Country names him Kamarag.

The President from The Undiscovered Country. The novelization gives his name as "Ra-ghoratreii". Commander-in-Chief Fleet Admiral Bill. The novelization for that movie gave him the last name "Smilie". This has given rise to "William Smilie" in other novels. Admiral Cartwright. Novels name him "Lance Cartwright". And who could forget Colonel West? Novels have given him the full name "Patrick West" while his mirror counterpart is named "Ivan West".

An unidentified command division crewmember of the Stargazer seen in Picard's memories on the bridge in "The Battle" is used in the novels as Gilaad Ben Zoma, first officer of the Stargazer. An unidentified operations division crewmember at navigation is used as Durand. An unidentified sciences division crewmember at the helm is used as Idun Asmund. And another unidentified command division crewmember is used as Christof Schuster.

Gul Macet from "The Wounded". The DS9 relaunch named him "Akellen Macet" and explained his "resemblance" (*cough cough* Marc Alaimo) to Dukat as them being cousins.

Kai Opaka who only physically appeared in "Emissary" and "Battle Lines". The DS9 relaunch novels name her "Opaka Sulan".

General Krim from "The Circle" and "The Siege". The DS9 relaunch give him the full name "Krim Aldos".

Lieutenant Commander Cavit, Chakotay's officially-assigned predecessor as Voyager's first officer. The novelization of "Caretaker" gave him the full name "Aaron Cavit", and subsequent novels followed with that.

An unidentified Bajoran Militia officer in "Rapture". He was the basis of the DS9 relaunch character Yevir Linjarin.

Lieutenant Hawk from First Contact. Section 31: Rogue named him "Sean Hawk", and the Titan novels have followed this. Also Admiral Hayes who reappeared in Voyager. The Slings and Arrows miniseries named him "Jeremiah Hayes".

Shinzon's viceroy in Nemesis. The novelization names him "Vkruk", and subsequent novels have gone with this.

 

[The Wormhole]

Also Admiral Hayes who reappeared in Voyager. The Slings and Arrows miniseries named him "Jeremiah Hayes".

As I recall, Jeremiah was actor Steven Culp's wish for his character, the Enterprise MACO Major Hayes to be named, as the character wore a nametag which said "J Hayes." The novels ended up naming him Joss Hayes though.

 

[Mr. Laser Beam]

^ 'Joss' could still be a nickname. Like if Hayes' real name is Jeremiah but he's just really into watching 150-year-old Firefly reruns.