RE: Slug Gun Scope?
If it's not a cantilever barrel I would suggest just using the open sights. If its a cantilever barrel I have a bushnell trophy 1.75-4x32 and am pretty happy with it. It's the cheapest scope I would get at 100 bucks.
As far as what power, depends on what kind of ranges we are talking about and how accurate your gun is. 4 power should be plenty for out to 100 yards on deer sized game. If you think you may have to take quick shots I would go with a low power scope or red dot, or better yet fiber optic sights.
As far as what scope you should get, there are tons to pic from, go with what you like and looks good to you. I would stay above 100 dollars with lower power scopes. The higher the power the more money you should spend.
By the way, a bushnell Elite is a great scope. It's the 50-70 dollar bushnell, tasco, simmons scopes I would stay away from.
Paul