In Australia, everyone is 'mate'.
Someone holds the door open for you? "Cheers mate!"
Getting petrol in the car? "Fuel at number 5 please mate."
Someone lets you in during busy traffic? *Mouths* "Your a bloody legend mate!"

Then as for your friends, anything derogatory (with guys at least) works fine.
"Oi d***head!"
"What the hell have you been smoking dip****?"

That's the way it is with males at least. Females, I am not sure. Nobody understands them. Except females. And they hate eachother.