Though, for long term results, a cat is best. They are rightfully scared witless by a cat and won't come near the place. The cat hardly has to even work - just be there and look menacing.
btw, Glen, you beat me to a photo like that...
P.S. Technially, a terrier will also work.
http://en.wikipedia.org/wiki/Rat_Terrier
A cat will work for Mice, but not for a rat.. Rats have been known to kill and eat the cat. A 3 pound cat is out classed by a 10 pound+ rat on the rats worst day. Snakes love rats...the bigger the rats get the bigger the snake grows to eat them. I have though "shot" 15 to 20 pound rats on Docks and wharfs in the pacific.