"!" is to tell players that the mob has been "Perma killed" by a GM due to a bug until the EQ Live team has a chance to check out the problem and find a fix for it.

YOu can kill the mob if you want and give the mob stuff, but you won't get anything from it.

The # I can only guess is for some development purpose. Since Verant filters out the # in the client. We've all seen what It does in ToFS, but it doesn't seem to mean the same thing from zone to zone. No idea why they do it, and I have no idea why they don't remove it either. (logic behind some kind of cookie makes sense I guess)