Like others have said, so many. But one stands out right now as I think about it.
When Jessica was about 18 months old, she got bacterial pneumonia and was very sick with it. When she finally came out of hospital, several things happened which meant I was more than broke and couldn't afford, well, life. I was a single parent and money-wise had about £40 per week for the two of us to live on, pay bills, clothes, heating etc.
So anyway, I was standing at the bus stop one morning next to this very elderly lady who commented on Jessica's residual cough. After some conversation, we somehow got around to how I couldn't afford to feed my daughter nor heat our home. Now don't ask me how she found out my address or anything, but a few days later she turns up at my door with a tall man carrying a HUGE box full of food, clothes and toiletries, plus toys for Jessica.
She did this a further 4 times throughout the year and I never was able to find her again to say thank you. But she pretty much saved our lives that winter.