Frightful Presence( Draconomicon, p. 105)
Like a dragon, your mere presence can terrify those around you.
Intimidate 9 ranks, CHA 15,
You gain the use of the frightful presence ability. Whenever you attack or charge, all opponents within a radius of 30 feet who have fewer levels or Hit Dice than you become shaken for a number of rounds equal to 1d6 + your Cha modifier. The effect is negated by a Will save (DC 10 + 1/2 your character level + your Cha modifier). A successful save indicates that the opponent is immune to your frightful presence for 24 hours. This ability can't affect creatures with an Intelligence of 3 or lower, nor does it have any effect on dragons.