Ireland and particularly the Irish language (Gaeilge) has a lot of them.

My favourite one in Irish is

"Tá mé ar mhuin na muice" which literally means "Im on the pigs back" This means that you are well or that you are having a good day etc. Sometimes people will jokingly say this in English too, usually to friends family etc

"How are you today?" "I'm on the pigs back"

There's loads of other ones too that people say, many of which probably have roots in the Irish language but we don't know since the Brits made it illegal to speak Irish during their rule of Ireland.

"You're gas!" They are very funny. Sometimes used in addition to craic (craic, pronounced Crack, is an Irish word for good natured shenanigans or fun) You could say "They are gas craic all together" Meaning this person or people is exceptionally funny or enjoyable to be around.

Some others

"I will in me hole" I will not do that

"I will, yeah!" I will not do that

"It's mighty tack" Of good quality

"Ah sure, you know yourself now" Kind of like saying 'thats how it is I guess'

"If there was work in the bed, he'd sleep on the floor" This person is very lazy

"She'd pull up floorboards looking for pipe" This woman is promiscuous/ horny

"Tis steep enough" Said when commenting about the price of something being high

"There's an aul nip in the breeze" Said if it is somewhat cold outside

"Tis fierce close" It's warm/ humid outside

"It's Baltic" The weather is very cold

"It's a massive day" It's sunny and pleasant outside

"He's a bit of a black guard" (black guard, pronounced 'blaggard') This person is silly, funny or may not be trust worthy

"I battered him" I physically beat him up

"He's an awful messer" This person is playful, foolish or silly

"I'm wrecked" I'm tired

"I'm tipping away" Usually said in response to 'how are you?' It means I'm doing okay, taking it easy

"How's she cutting?" How is it going/ how has your day been

"Now we're sucking diesel!" Now we are doing well! Can sometimes be used as an exclamation when something goes well. If you fixed a problem or are making good progress.

"I'd do be at that the whole time" I do something regularly or habitually. Sometimes shortened into fewer sounds/syllables, sounding something 'I'd-d'be at dat the whole time' though that would usually be an older person with a very strong accent. Most Irish people these days would have a comparitively mild accent.

"Tis pure shite" It's very bad/ of poor quality

"A sniper wouldn't take her out" This person is unattractive

"He'd get up on a gust of wind" This person is very horny/ promiscuous

"I'm as sick as a small hospital" I am very unwell

"I'm as sick as a plane to Lourdes" Also means I am unwell. Older people like to travel to places of religious significance hoping for a miracle to heal them if they are sick or unwell.

"I'm as shook as a hand at mass" I am very stressed/ tired/ worn out. Comes from 'offering a sign of peace' in Catholic mass, where you shake the hands of everyone sitting next to you, in front and behind you.

There's a ton of others. They can also be quite regional. I'm from Cork in the south of the country, so these ones tend to be more popular here. There are other ones more commonly used elsewhere in Ireland.