I'd go for Zane Grey Theater, in which several episodes were pilots that spawned such series as Trackdown, Black Saddle, Johnny Ringo, and The Westerner. Crime dramas like The Detectives starring Robert Taylor, Dante, starring Howard Duff, Target: The Corruptors, and The Dick Powell Show/Theater...
I would cast my vote for Pistols-n-Petticoats, a western sitcom which has seen six episodes released on DVDs albeit in B&W instead of color. TMG should go for the gusto to get that one-season show!