According to Askmen.com these are things that guys (even buddies) do that completely annoy other guys.
Excessively revving your engine
Off colour humour
Bragging about cheating
Flirting with another guy’s girlfriend
Going too far (teasing and razzing)
Not having proper gym etiquette
Being a snob
Starting a conversation at the urinal
Abandoning friends for a girl
and the #1… Changing around women. You know when he acts one way around the guys but as soon as a beautiful woman enters the picture he completely changes? Not in a good way either.
Can you think of any others?