Rowan picked up on "S###" and "F###" pretty early on. The more we tried to tell him no, the more he used them. Finally, we would just start telling him those weren't nice words and only grownups get to use them... that seemed to work because he stopped saying them pretty quickly as soon as he stopped getting the reaction to them.
Now his favorite phrase is "Jesus!" or "Jesus Christ!" My father's the only one taking an issue with that one.
Nice. Very ####ing nice.