When Ian Arnstein sees a ten foot, two headed cobra above a temple, he asks himself:
"'...where's Conan when you need him?'"
-SM Stirling, On The Oceans Of Eternity (New York, 2000), Chapter Twenty-One, p. 435.
One place he is is in Conan The Rebel by Poul Anderson. Arnstein also refers to Howard Fast's Spartacus. Fast wrote that Spartacus' name would be remembered and sometimes shouted. I have heard it. Fast's Spartacus said from the cross, "I will return and I will be millions." See here.
Conan and Spartacus are an interesting contrast, a fantasy hero and a historical figure.