Weasels are quite titchy! We saw a couple playing in a lane last year, sweet - certainly not frightening. I had a middling-sized rat dying in the middle of my lawn recently. It must have eaten the poison and, oddly, come into the open to die. It wasn't well and was swiftly dispatched by OH with a shovel.
The biggest rat I ever saw was in France (I'd an ex-farmhouse with barns and hens, so rats were standard). Fortunately this one was dead, it had fallen into a cistern and drowned, because it was huge, a really massive, pregnant female. I didn't measure it, but easily twice the size of the one on the lawn.