I had the pleasure of seeing a Least Weasel scurry past the front of the garage yesterday, going from one pachysandra patch to another. They are not uncommon in their multi-continental, northern-hemisphere range, but I rarely see them. It makes me happy when I do.
Most often, they are seen hurrying across a country road.
Least Weasels like to be in cover, not out in the open. They are both daytime and nocturnal hunters, and active all winter in the snow, when they have all-white fur.
They are said to be the world's smallest mammalian predators, around 8-9" long. Bloodthirsty little guys.
On further thought, that guy could have been an Ermine. Not sure I can tell the difference because they move so quickly.