Sounds like you have some experience, I especially like the key dropping suggestion. Since you brought it up how would one train a dog to distinguish between squirrell in yard vs. stranger at door?
After reading these posts my personal choice would be a german shepard however I will need to get a bigger place first I think. My Grandfather trained this breed back in WW2 and owed his life to one.
Thanks all for the informative responses.
A.J.: You're going to need a bigger gun!
Riff: That's what I like to hear. How much bigger?