If you're a rogue, You must have a killing macro. End of Story. Every rogue has one
Ninjaasassin
Getzskills
Oggrandpurp
(Myself)
Okay so not every rogue, but these are the one's im aware of lol.
If you plan to pvp, a killing macro is to simply annoy the living daylights out of them. Especially when you farm them!

Best of Luck!