| Vaergoth |
Honestly, I don't know if cribbing from other games is either suggested, frowned upon, strictly disallowed or what, but I think what Exalted does with Charms is a good starting point for mythic abilities. It's been said and said, but mythic needs to make you different, not better. Charms in Exalted sometimes make you better, but usually they have unique effects that couldn't be accomplished with skill checks.
Maybe spells, supernatural abilities, and extraordinary abilities are the way to think about mythic abilities. These things present those who have them with new options, which is exactly what mythic needs. Maybe the mythic marshal can use rally to negate any and all fear effects from everyone around him. Through Shot and Wall Smasher are steps in the right direction.