96 in a 30 (though I dispute there is NO need for it to be 30, there's no schools or shops etc, and it's in a small sleepy village with clear view all along the perfectly straight road).
Bike copper standing behind a skip with a speed gun.
Got off with it completely as I argued (politely) the speed limit & could prove I was being very observant by telling him the phone number etc of another skip positioned a couple of hundred meters back (didn't say I'd been there only yesterday & remembered which company the skip belonged to - and just happened to know their number). I also told him about all the cars parked on the road, and even one of the numberplates of those cars (which is owned by a mate)
He said that because I was being so observant, consider this my lucky day, and hinted that he thought it should be a 40 zone, but he couldn't say that for some reason.
EDIT: I've also undertaken an unmarked police car doing approx 75mph in a 50zone. All he did was flash his blue lights & shout "slow down on that thing or you'll kill yourself." I nodded & waved, he carried on driving. So that doesn't really count for this thread.