The top choices in my opinion are 1 Mossberg 500 12g 2 Remington 870 pump 12g They are both highly customizable with aftermarket parts, and each are very reliable and relatively speaking inexpensive. I also like the winchester 1300, its all up to you. You might also check out the more expensive models like the benelli, spaz 12, saiga etc. It depends on the rounds you wish to shoot also, the mossberg handles 2 3/4 and 3" shells which is another reason I have it as top choice.
As do I. My favorite is the Mossberg because of it's safety position, but if that weren't a factor I'd go with a Winchester 1300. They just "feel" better. You can also pick up an older 1200 cheap. You don't really need 3" shells for HD.I prefer my mossy 500 for the safety position