In addition to my nomination of Jose Torres, who I think was one of the mainstay utility man across the whole history of spaghettis, from cameos to a leading role in the waning days of the genre, and exhibits great acting ability in films like Tepepa...
I'd also like to re-nominate Alex Cox in the Misc. Contributor category. In addition to being a tireless beater of the drum for films like Django and Django, Kill!, Cox has carried forth the aesthetic and spirit of the spaghetti western in films like Straight to Hell and Walker, and has written, I believe, one of the finest treatises on the genre in his 10,000 Ways to Die.
Though I find much to quibble with in Cox's reviews of the films, his contextualization of their creation and insights as a filmmaker are proving invaluable to me as I go back through some of my favorites.
Here's a great interview with Cox, courtesy the SWDB.
Here's a brief paean to the genre in the New York Times written by Cox.
Here's Cox introducing Face to Face on Moviedrome.