Aimpoint Red dots are the best. But they cost mucho dinero.

I use a Bushnell Trophy red dot scope on my slug gun. I've used other red dots before, and nothing compares to the Bushnell so far. Crystal clear image, has not fogged or the like at all...and we've had some pretty cold days here in NY.

I picked up the Bushnell @ my local BPS for $80, that included mounting and boresighting. Although, the guy there could use a lesson in boresighting. The first shot I took was good for windage, but was 3 foot high!! It's hitting now.