PitrDeVries said:
"CLEANSE! PURGE! KILL!"
For added effect, say that in a crowded area wearing a hazmat suit.
Dechef said:
ORCS ORCS ORCS ORCS ORCS ORCS
Orks:
-We'ze the Orks an' you iz not
-Orks is the biggest and the the strongest
My favourite is still from dark crusade when orcs see elder:
"Bah! Puny elder send half the boys home"
Chaos:
-"Despair, for I am the end of days"
-"It is as though a thousand mouths cry out in pain"
-"MAIM KILL BURN! MAIM KILL BURN!"
-"Sanity is for the weak!"
Guardsmen and spacemarine have some good ones too
-"Fear denies faith."
-"I Fear no evil...For I am Fear Incarnite!"
Sorry for the quote spam but I figure dawn of war battlecrys fit quite nciely here and these are my favourite.