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1.
An Australian expression - if you think something is awesome, brilliant etc. then it is said to be the duck's guts.

Synonyms (see below) include the bee's knees, the cat's pyjamas, or, strangely enough, the cat's arse.
My new cricket bat is the duck's guts.

Look at that pony-tailed wanker in his BMW. He thinks he's the ducks guts.
by Choda Boy 57 August 12, 2006
 
2.
The best there is - the best of breed
Those wheels are the ducks guts
by evil_roy February 24, 2005
 
3.
Australian slang for 'Great' as in 'The Bees Knees'

Famously used in the 1979 Australian Film 'Mad Max'
*Just as Max is shown the Pursuit Special, in particular the enormous supercharger protruding from the bonnet

Goose; "You can shut the gate on this one Maxxie, Its the Ducks Guts!"
by Chumblet January 28, 2014