stryx: Does the user with the highest reputation get anything? What is the benefit of having a high reputation? I don't even remember mine. That probably means that I have a low one...
Zchinque: "5. What is this “rep” thing on the forums?
Rep is the user's reputation rating, showing how respected and well-known you are in the community. You can quickly estimate a user's rep by looking at the number of stars next to their rep value. Getting one or two stars is fairly easy, while five stars is a serious achievement. Those who earn maximum reputation can expect some kind of nice bonus (surprise, surprise! :)."
Taken from
here.
Edit: Damn you, forum software!
Apart from getting 5 stars, I don't think I've ever heard of anybody getting anything special for having 5 stars. I suppose they might be keeping it secret, but overall I doubt it.
I think that's probably from when the site was first started and I doubt there's any benefit to having that 5th sttar now. Also, being downrepped for anything other than spamming seems to be mostly used as abuse.