People using the bus lane when traffic is really heavy
In stark contrast, something that really irks me (yes, IRKS!) is when I'm sat in three lanes of heavy traffic, and there's an EMPTY bus lane next to me that nobody is allowed to go in. I don't know if anybody has ever been over the Stairfoot roundabout near Barnsley, but that's got a bus lane right through the middle of it, and in all my time of living here I've yet to see a bus use it.
Another thing would be when you buy a sandwich from the shop and you get it back to the office and discover that the bread has gotten wet and you are left with a partly dissolved sandwich that is the texture of slime.
This happens a lot in Cooplands. Buy a sandwich, then by the time you've got back home/office with it, and open it, it isn't what you ask for. Why don't they either listen to what you want - this is sandwich making; it isn't difficult, or show it you before they bag it?! They're very quick to show Margaret in the back room your tenner before sticking it in the till!
Oh... here's a good one.
People that drive at 40mph in a 60mph limit. Then, when they get into a 30mph limit, they still drive at 40. WHY?!