Another vote for the H&R Deluxe Slugster in 20 or 12 gauge.

Reasons why it is better than the pumps (Remington 870)
1) More accurate (a tack driver)
2) shorter action (no pump action which leads to a significant length in the gun overall)
3) integrated scope mount
4) less recoil (it is heavier)
5) less expensive
6) less cleaning necessary (it is a break open with a hammer)
7) in some respects more safe (if you don't cock the single action hammer you are real safe)
8) better fit and finish then most pumps - "feels" like a better gun

only negative is if you are going to do a lot of walking... It is a pretty heavy gun, although the sling fits better on it then most pumps.