palooka
weisenheimer
bubba
goombah
yooze
daddy-o
sport
goodtime charlie
paisano
friend
compadre
amigo
hey, old [their last name]
I remember a Dave Berg “Lighter Side” in MAD magazine where Joe Schmo greets some local big shot, and Big Shot responds “Hey, Mac!” Whereupon Mr. Schmo turns to his wife and says all excitedly “did you hear that?! He addressed me by my name! ‘Mac’! Maybe I’m not such a schnook after all!” as she listens all abeam. Then in the next panel, Big Shot returns the greetings of every other with “you too, Mac!” “pleasure’s mine, Mac!” “likewise, Mac!”, and Schmo sadly droops as his wife’s approval turns to scorn.
Not to brag, but I was always pretty good at predicting those Dave Berg twists.
Additional UK info: the people of the north-east of Scotland speak an unusual variant of English, with rather a lot of words unknown elsewhere. In those parts, any male human will be addressed as “loon” (no connotations of insanity: it’s more or less equivalent to “lad” or “fella”); any female ditto, as “quine”.