I don't consider "Hell" a swear word. But I wouldn't say it in school!
Ahem: "GIVE HER HELL FROM US, PEEVES!"
Psyduck's right, that's FUN to say... especiall considering the "her" is Umbridge. *Shudders* That woman creeps me out more than the Death Eaters...
You know, Fred didn't even MEAN it as a swear word. He meant it like "havoc" or "major trouble". He didn't mean it like "heck".