One we all know – but you need space for this!
Someone is the grandma (or grandpa) who stands at the far end of the room, with their back turned to the rest of the group. The rest of the group stands at the opposite end of the room in a line. The idea is that they have to sneak up on Grandma. But at any point, the grandma can turn around. When they do, everyone has to freeze!
Anyone seen moving by grandma is either ‘out’ or sent back to the beginning again. I’ve noticed it’s a good one to play with a brand new group to see what sort of characters are there – you have the children who play by the rules and do their best to stand stock still, and there are others who just rush forward, whether grandma is looking or not.