I have this one on my new Turkey gun but it would be perfect for a slug gun as well..............oneclickshooting.com has them for $139 with free shipping and they threw in a lens pen and covers.
They even have a lifetime transferrable warranty ala Leupold.
http://www.muelleroptics.com/products/MU2732IGR.html
http://www.oneclickshooting.com/proddetail.asp?prod=8932812