A pet crayfish named Clippy II and an apple sn...

A pet crayfish named Clippy II and an apple snail in a freshwater home aquarium (Photo credit: Wikipedia)

X

XXXX : pronounced Four X, brand of beer made in Queensland

Y

Yabber : talk (a lot)
Yabby : inland freshwater crayfish found in Australia (Cherax destructor)
Yakka : work (noun)
Yewy : u-turn in traffic (“chuck a yewy at the next traffic lights”)
Yobbo : an uncouth person

Z

Zack : sixpence (5 cents) – “it isn’t worth a zack”, “he hasn’t got a zack”