Well if you are referring to non-lit fiber optics then the Impact sights are probably the brightest you are going to get. I have been using my Toxonics Solotrak with light kit when I hunt out of the blind. It helps immensely.

I did notice though that Impact has a new, relatively inexpensive, fiber optic sight on the market which has a small light built into it. It is not bright enough to create a glare on the pins and yet it adds a sufficient amount of illumination to be effective.