I have always had an emergency box in the pantry. It has a lot of the things in the 'grab bag', and also things like dried and tinned food, bottled water, candles, a primus stove (and gas), paracetamol, tampons (a bit aged now , loo roll, a wind-up torch, and even a pack of cards, which I put there when my children were small, to give them something to do in an emergency.
I put it together long before the vote for Brexit, in case there was a power cut, a flood, getting snowed in - whatever. My grandmother had one in the war, in case they had to leave the house in an emergency, and my mum followed suit, so it seemed a natural thing to do. I check it every few years to make sure the batteries are working, and the food and drugs are roughly in date.
My box isn't really a 'grab bag', though, It's far too heavy. It's more case of knowing where to look if the power goes off, or if we suddenly had to leave the house to camp out in a church hall for some reason. There is plenty of food in the pantry proper, but it's reassuring to know that I can cook the things in the box if the oven and microwave don't work.