Master Chief was never a guest character in a Soul Calibur game, but I think many people tried to make him in the character creation mode.
The guest characters in Soul Calibur 2 were different depending on which console version you got. PS2 got Heiachi, Xbox got Spawn, and GameCube got Link. Of course Link was the best one to get.
In Soul Calibur 4, Star Wars characters Yoda and Darth Vader were guest characters along with a new one from one of the Star Wars games out at the time.
Soul Calibur 5 and 6 had guest characters from Assassin's Creed and The Witcher.


