Free: Contests & Raffles.
Defense from? From what you've described I'd say .357 mag 6" barrel. There's plenty of good semi auto's in various calibers that would be good too. I just like the simplicity and power a medium to large bore revolver offers.
Glock 20 10mm covers both of your defense needs
Revolvers out in the field, you just cant get a powerful enough cartridge in an auto thats small enough in a weight vs power combo. Autos for in town.