Mylor and I had this conversation some months ago:
"Benspit!" = with the same convenient initials of BS, signifying something that one believes is not true e.g. "Sir, that statement is pure Benspit!" or something that is badly-made or defective, as in "This battle hammer is a piece of Benspit".
For greater emphasis, extend the oath e.g. "By the Dribbling Saliva of Ben!"
I often simply swear "By the Light" or "In the name of the Light." Short, sweet and to the point.
Of course, Valornian (?) is not Venus's first language, so after having been told off for using "Damn!" (which I still think is kind of OTT) when I land on the floor of the inn I often swaer "K'znch'ai!", which at least has enough guttural sounds to be a good swear word. Anyone with creative interpretations as to what this may mean can PM me with them