OK, now THIS is interesting. There's a list of story assignments made during Season One. It includes a number that were abandoned and never produced (at least, not under the given name).
So, in some alternate universe, TOS Season One included:
Warrior's World by Stephen Kandel
The Machine That Went Too Far by A.E. van Vogt
Chicago II by George Clayton Johnson (an early attempt at A Piece of the Action?)
Alien Spirit by Norman Katkov
Untitled by Jack Guss (I'm willing to bet that wouldn't have been the final title)
Journey to Reolite by Alfred Brenner
Rites of Fertility by Robert Sheckley
From The First Day To The Last by John D.F. Black
Sisters in Space by Robert Sheckley
Portrait in Black and White by Barry Trivers
Rock-a-Bye Baby or Die! by George Clayton Johnson
The Squaw by Shimon Wincelberg
Accident of Love by Allen Balter & William Woodfield
Dreadnaught by Alf Harris & Jeeli Jacobs
World of Warriors/Tomorrow the Universe by Paul Schneider(another attempt at Kandel's earlier Warrior's World?)
In all, there were 45 assignments handed out for the 29 episodes produced in Season One (several stories turned up in later seasons, like The Omega Glory, Amok Time and Friday's Child)