This is a marvellous thread!
“Actually, a contender for the worst one. Jobbie. I know that as a juvenile word for poo, shouted across a playground or by drunk people "yah jobbie!!" Unfortunately quite a few senior people in my work use it as a word for "small task". I have to stifle a snigger every time...”*
Oh, that would just be non-stop hilarity! I love the idea of the CEO’s answering machine message saying snootily “I’m afraid I can’t come to the phone right now as I’m just in the middle of doing a little jobbie” 
And yes, I've had my literacy questioned after using the word outwith. I feel vindicated!!
It’s a perfectly normal Scots word, albeit not known further south. Does anybody remember the old hymn ‘There is a green hill far away, without a city wall’? That’s basically the same usage (but with the syllables swapped around) – it doesn’t mean that the hill doesn’t have a city wall (why would it?), but that it is outside of the city wall.
Other Scots/Weegie favourites of mine are greetin’ (crying), we’en (child = ‘wee one’) and puggy (pub fruit machine).
You're right ."Ar bay" is I'm not.
The other Black Countryism that causes similar confusion is the omission of the ‘n’t’ from the end of don’t, pronouncing it like ‘doe’ (as in deer). Slightly confusing when spoken, but completely baffling when some will then go on to write it as ‘do’, making it apparently mean the exact opposite – “I do like it” meaning “I DO NOT like it”. I heard one BC comedian once say that the singer Dido is known locally as ‘Diane: stop it!’
Cock as a term of affection, apparently this isn’t really a thing outside of the Black Country
Jasper Carrot once did a rather silly (but still very funny) routine about him smuggling a counterfeit ‘designer’ watch home that he’d bought from a dodgy market stall whilst on holiday, by wearing it on his, erm, gentleman’s appendage. He then bumped into an old friend at airport security who panicked him by asking loudly “Jasper, me old mate – hey, 'ave yer got the time on yer, cock?”
The East Midlands (Nottingham) dialect sadly underrated I think - and no actor on earth can do the accent apart from Vicky McClure and Su Pollard.
Don’t forget also the wonderful Lauren Socha. Granted she doesn't have the best ever name for a premium brand of cooking fat, though
‘Trump’ meaning fart is another one that doesn’t seem restricted to just one locality, but is far more commonly used and understood in the North and Midlands. A surprising number of British people have never encountered it, even though it’s basically just an abbreviation of ‘trumpet’, and hilarity ensues when they only know it as a term in Bridge! When DJT became the US President, he was very proud of his name as, to them, 'The Trump' means ‘the Ace’, ‘the Boss’, ‘Top Dog’ etc. and a lot of his fans were horrified that Brits had chosen to grossly disrespect and insult him by ‘inventing’ a ‘new’ meaning of his name to mean something vulgar, as had previously happened domestically with Rick Santorum. Nope – we had been trumping for a very long time, long before The Donald was even born