Crimson pygmy barberry. It is non-native. Some people say it is invasive, but where I lived before (a couple houses ago now
) there was a crimson pygmy barberry hedge for years and it never spread or popped up anywhere else.
It has very sharp thorns. You never want to leave pruned branches of it lying around, because the thorns can drop off and then just sit there invisible waiting for a vulnerable foot. It keeps that color all through the growing season, but it is deciduous, so bare in winter.