Fella: The ultimate insult.
Within certain circles of the British Military the word 'cunt' is so regularly used it has lost all meaning and causes no offence whatsoever.
The word 'fella' is now commonly used as a replacement and holds equally insulting attributes as the word 'cunt' does to most normal people.
Oi Fella! Wind your fucking neck in or I'll stick this baton straight through your ears and ride you around the place like a fucking horse.
(NB: Hold particular weight when used to address a member of the Royal Engineers, they really like it)