A few of my personal favourites.
My mother had a few that stuck with me through life
Her response to bluff, bullshit and equivocation; "You're all wind and pee - like the barber's cat".
When I first tried my hand at singing I was told, "If you were singing for shit, you wouldn't get the smell of it", late adapted to, "not bad, for a beginner".
She described someone of small stature as; "He has to stand on tuppence to look over thruppence.
A local dancing master around here was asked how a now internationally famous veteran box player who as going to him to learn music was progressing - "Ah, he's doin' his best, poor feller".
Dubliners have a couple of nice ones for people who have done them a good turn: "Your blood's worth bottlin'" or "You're handier than a small pot"
Liverpool bar staff had a string of sayings to deal with customers who couldn't hold their drink - I heard one barman ask a man who had spilled his beer all down his shirt-front, "Do you intend to drink that or wear it?"
The Radio Ballads team spent a time recording miners in Wales and in the N.E. telling stories for 'The Big Hewer' - they were told of a Trades Union leader who had sold out his men during a strike.
He addressed a pit-head meeting with the opening line; "I suppose you think I've sold you out to the bosses?"
A voice shouted out from the body of the hall, "No - they buy gold, not shit".
During a late-night conversation we had with Joe Heaney in a tatty caff in Euston, not long before he died, he complained about growing old, "It takes me all night to do what I used to do all night".
Jim Carroll