Out of curiosity, which PC games can you think of that were created to be played with keyboard controls in mind and either don't have mouse controls or only put them in as an afterthought, not as central gameplay element? I'm particularly curious about older 3D action games like FPS and TPS without mouselook, but anything's fine. Brownie points if the games are on GOG, or if you can even point me to a good GOGmix if there is one about this topic!

Duke Nukem: Manhattan Project

Dead Reefs

TMNT
Prince of Persia Sands of Time

not on GOG but, Dreaming Sarah
got it for 0.35 cents on Steam, dunno the actual US price.

Gothic 1 and 2 come to mind .

Roguelikes have traditionally been very keyboard-centric.
And the Doom series plays just fine with only the keyboard. I think.

Risk of Rain
mostly mouse pointer is for tool tip.

Might and Magic 1 and 2. (I believe 3 through 5 can be played keyboard-only as well.)

Ultima 1-5. 6 uses a mouse, but I think it's not required,

Pool of Radiance and other games using the same engine. (Later games added mouse support, but it doesn't seem to be required.)

Bard's Tale 1-3. Some versions (including the versions of 1 and 2 included with the newer game with the title, as well as the DOS versions of all the games) have mouse support, but it isn't ever needed. Note that the DOS and Amiga versions of 3 should be avoided; there are way too many fun-decreasing bugs.

Not on gog.com, but Wizardry 1-5 use only keyboard. Of note, Elminage Gothic plays like the early Wizardries, but the interface is built around using a game controller (but a keyboard will work fine since the game is turn-based).

Hammerwatch

Maybe also Rune, Blade of Darkness and Tomb Raider 1-4? What about Duke Nukem 3D? Dark Forces? Does Indy: Emperor's Tomb require mouse controls?

The Might & Magic-series can be played flawlessly with keyboard only. But I have only played MM 1-6, so I don't know about the last three.
I finished Duke Nukem 3D on the hardest difficulty using keyboard-only controls. It worked very well :)

The Adventures of Shuggy

Ittle Dew

Carmageddon 1+2.

Most of Racing games.
Burnout Paradise Ultimate Box