F*ck
F*ck was a profane word, sometimes used as a synonym for sex.
The word was used in the expressions "what the f*ck?" (TV: Everything Changes, Countrycide) and "f*ck knows", (TV: Random Shoes, End of Days) and the terms "f*cker" (TV: Countrycide) and "f*ck buddy". (TV: Out of Time)
Gwen Cooper once shouted, "F*ck you!" at Jack Harkness after he taunted her for her affair with Owen Harper. (TV: End of Days)
Owen used the word to call a group of cannibals "sick f*ckers". (TV: Countrycide) He also used "F*ck knows" in response to a question about Eugene Jones. (TV: Random Shoes)
Rhys Williams once in a fit of rage told Gwen to, "sit the f*ck down!" (TV: Combat)
Facing a hostile Nostrovite in the form of his mother, Brenda Williams, Rhys exclaimed "F*ck!" when the chainsaw he wielded failed to work. (TV: Something Borrowed)
Upon discovering a bomb, Allen Shapiro gave his last words, "Oh, f*ck!", immediately before being caught in its explosion. (TV: The Blood Line)