We assume you mean “who were the faceless actors” to play Blofeld, but for the sake of completeness we`ll list *all* the actors. The decision not to show Blofeld`s face, and just have him pet the white cat, was clever, even brilliant. Oddly, nobody has ever claimed credit for this idea.
“From Russia With Love” (no face) Eric Pohlmann (voice)Anthony Dawson (body; Dawson played Professor Dent in *Doctor No*)
“Thunderball” (no face) Joseph Wiseman (voice; Wiseman played Doctor No in the film of the same name) Anthony Dawson (body)
“You Only Live Twice” Donald Pleasance(face) Note: Jan Werich had been cast to play the part, but fell ill. Donald Pleasance was a last minute replacement.
“On Her Majesty`s Secret Service” Telly Savalas (face)
“Diamonds Are Forever” (Charles Gray (face) (he also played Dikko Henderson in *You Only Live Twice*)
“For Your Eyes Only” John Hollis (no face)
“Never Say Never Again” Max Von Sydow (face)