Actually in Darksiders, shortly after you get that horn, you are jumping from piece of broken bridge to piece of broken bridge. This big demon follows you and it fights you on one of the pieces. It has a really sporadic attack pattern, and moves really slowly. Problem is, you have to get close to him to attack him, but I found that if I used the horn to make him stumble, it also did a bit of damage, so I just tapped the R2 button to use the horn, and I beat him with absolutely no trouble. I haven't tried it on any other bosses yet (he was sort of a miniboss, not sure at all if it will work on anything else) but it made me think "Wow, did no one do this during a playtest?"