Oh, I got to hurry before slugman comes on with his single shot recommendation.
I have a 870 slug, and a gold slug. One thing I can tell ya, the gold's semi-action really takes the kick out of slugs. I don't mind to shoot it all day. (if I could afford the slugs). The 870 is a royal pain. Litterly.
When looking for one, get a good recoil pad. They ain't much and worth it. Also cantilever barrels are the way to go. I only paid 650 for my gold a few years ago, but recently prices have skyrocketed. I wouldn't pay the 850 or so they are asking for now.
I would go with a good 1187 first. Barrels are much cheaper and I don't see much accuracy difference in my 870 and Gold.