Richard Harrison, an American expatriate actor who at the time was best known for sword-and-sandals roles, had starred in a couple of Italian Westerns made prior to
Fistful. According to Schickel's
Clint Eastwood (p. 131):
Harrison already had a commitment for the spring of 1964, but he had seen Rawhide, liked Clint's work in it, and recommended him to Leone.
This anecdote has been frequently repeated (including in the IMDb), but its authenticity is questionable. Christopher Frayling reports (
Sergio Leone: Something to Do with Death, p. 134) that Leone never considered Harrison for the part, although his producers, who had him under contract, wanted him for the part of Joe.
But Leone turned him down: "Harrison cost only $20,000, but he still didn't appeal to me."
Leone had his heart set on an established American star ... besides the above-mentioned Fonda, Bronson and Coburn, Cliff Robertson was considered, and the producers thought of offering the part to Rod Cameron. Coburn (who wanted $25,000), Robertson and Cameron were too expensive, Bronson turned Leone down flat (as noted above), and Fonda's agent didn't bother to show his client the script.
According to Frayling, the tip to Leone about Eastwood came not from Harrison, but from Claudia Sartori, who worked in the William Morris Agency's Rome branch. She arranged a screening of a
Rawhide episode for Leone, and when he reacted with "This man, with a vacant look on his face, in an unwatchable film about cows?" she retorted that he was on his way up in the U.S. ... and besides, he would take the job for $15,000. So, for a fistful of dollars, a star was born ...

However that may be, Richard Harrison seems to have had a long and fruitful career, mainly in European-made Westerns and Hong Kong-produced kung fu movies, but I don't recall that I've ever seen him in anything. Anyone?