Following off topic at http://www.ww2incolor.com/forum/showthread.php?t=4493&page=5 , here’s what happens when knackers and kangaroos breed, in WWII and now.
http://home.brisnet.com.au/~dunn/ozatwar/gulfscare.htm
http://www.diggerhistory.info/pages-army-today/state-regts/norforce.htm
http://www.abc.net.au/message/tv/ms/s1222121.htm
Curtin’s Cowboys, mentioned at the end of the first link, is the best single treatment of the original Nackeroos.
And pursuing another aspect of knackers, sans kangaroo, are immortal lines such as:
The boy stood on the burning deck
His pocket full of crackers.
One went off between his legs,
And blew off his [insert preferred adjective] knackers.
Or …
… Maybe I’d better not. It involves a bishop and balls and stuff. 
Is the Australian ‘knacker’ as in ‘mate’ used, because you are equally fond of both varieties?
Well, knackers come (no pun intended) in pairs which involves both varieties, so it’s a bit hard to be more fond of one than the other. Although the left one is reputed to be bigger and jucier than the right.
I wouldn’t know, because a bloke who’s fond of knackers would be a poofter.
Given another thread where ‘poofter’ upset someone about it offending bum bandits, poo punchers, fudge packers, turd burglars, fart stoppers, and so on, I’ll just say on behalf of the average Aussie bloke that we couldn’t give a shit (no offence intended to poofters) about knackers as long as you’re a mate.
Mate.
Knackers. 