I have shot whitetail deer with a 9MM, and whitetail deer and a muledeer with a 45ACP. The 45ACP is my favorite handgun... but I was really unimpressed with its performance on deer sized game. I highly recommend you go to the 44 Mag. I have taken several deer with it and it is a much better performer.
As has been posted above a 45ACP for the "city" and a 44 Mag for the "country"