I'm coming to it late, but my guesses would be John Dehner, Robert Vaughn, Tim O'Connor and Dean Stockwell. Of course, if you mean that each person got killed in their SECOND episode and survived in their EARLIER one, Dean Stockwell would be wrong.
d'oh! Last Salute is kicking my ass, I need to bite the bullet and watch it already. Dean Stockwell was my second-to-last quiz answer, only one left...
Wilfred Hyde White
The late great Anne Francis!