Funny how the game has changed so much. I can't think of a single pitcher now throwing only knuckleballs, although many have incorporated the knuckle-curve. But there were a plethora of them years ago. I remember the Neikro brothers, Joe and Phil did, RA Dickey, Tim Wakefield, Charlie Hough, and of course, Hoyt Wilhelm. Then I remember Jim Bouton throwing it with the old Seattle Pilots, while he was writing Ball Four, still a great baseball book.
Do you remember Steve Hamilton as a Yankee throwing his eephus ball? I was reminded of that just the other night when the Cubs brought in a position player to pitch after the Yanks had scored 17 runs, and threw one to Kyle Higashioka, who promptly deposited it into the left field stands.
Here it is, if you missed it:
https://twitter.com/i/status/1536090617830178816