A few years ago we passed 2 girls on nice road bikes faffing with a puncture (3 of us also on road bikes) offered support, they declined, in quite an agressive "we're fine, sod off" manner, came back past a good 40 minutes later and they were still there!
I once stopped to help some chap who'd broken his chain. He had a cheap multi tool with a chain tool, but had no idea what to do. I was helping him, and broke his chain tool (I very rarely carry one on the road), felt really bad but there was nothing I could really do other than apologise and ride off!
Stopped to help some other fellow once too who had a puncture in his spare tube on his MTB, I was on the road bike, so there was nothing I could do, but I'd have felt mean riding past.
Helped someone reassemble their headset once on Pitch Hill, their headset was loose, and I'm not sure how, but they'd dismantled the whole thing and didn't have a clue what to do!
Stopped in my car a few times to lend a track pump to folk struggling with a minipump at the side of the road too.
I'm just too nice.