My first choice for a deer gun would be the Remington 870 12ga.
2nd choice, an Ithaca model 37 DeerSlayer.

There's a good combination package available from Remington for the model 870.
It'll give you a rifled slug barrel, and a barrel for shot (BB). Following is a link to the
Remington website on this;
Remington Express Combo,
Link: http://www.remington.com/firearms/shotguns/870excmb.htm