[Controversial]

The greatest gore scene in a horror movie (anything from "Saving Private Ryan" doesn't count, because obviously that can't be beat with Speilberg's budget) would have to be the exploding head in William Lustig and Joe Spinell's "Maniac". Tom Savinni (who's head that was, by the way) was a true artist with gore effects. That movie defines a "true" horror movie. And that scene even 25 years later is absolutely beautiful.