Simmons ProDiamond 4x32 fixed scope. Simmons has a less than stellar reputation, BUT this particular scope, designed for shotguns, has received very good reviews, particularly from the muzzleloading crowd. It's rugged, clear, and easily good for shots out to 150 yards. It's only about $60-70.
I've used mine for about 5 seasons shooting pretty stout loads both in the field and at the range. It's held up great.