To  set the ball rolling...

My favourite of all the original Spoonerisms is still, "The Lord is a
Shoving Leopard.

And from the parachute club, over fifty years ago, the instructor
screaming at some poor unco-ordinated student who just couldn't get
his hands to obey when re-packing a chute, thus reducing the tangled
rigging cords to something resembling porn for squids,  "Why are you
such a cucking funt?"  Followed by a blank look and then roaring
laughter as he realised what he'd said.

Gyppo

I have to go back almost 60 years, to a geography class at school and a 12-year-old girl so anxious to show off her knowledge that, when the rest of us were wondering what the three staples of British cereal production might possibly be - I'd got as far as Cornflakes and Weetabix - she shouted out, "Wheat, barts 'n' oley!" 

Nice one, Jo.

Anyone else?

I believe I saw a fine example on a protest poster some years ago. Buck Frexit!

My old graphic design tutor used to use spoonerisms to complement his dyslexia. He was hilarious. Smug druggling was one of his creative laugh out moments

One of Mum's.  She was a bit dubious about a group of youths hanging around by the river.  "They're up to something, and there's a funny smell.  I think they're poking smot."

Gyppo