Ripper
Excellent.
Person 1"Got us front-row seats."
Person 2"You little ripper!"
You'll also hear
You little rippergreat news!
Where it's from
From the old British slang ripping, meaning excellent.

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While you're here
You're a good person. Said to thank someone, or to praise them to others.
Loyal and thoroughly Australian.
He is as good a person as you will ever meet.
Very fit and strong.
Excellent. Old-fashioned now and mostly used jokingly.
Something or someone excellent.