Looking for HP based ability?

Is there a default wc3 ability that takes some HP instead of MP to activate?

I don't think so. Unholy Frenzy doesn't really count, because it takes health overtime, but mana on the initial cast. That's the closest spell I can think of.

There is no such ability.

By default I dont think such an ability exists.

But Self targetting Thunder Clap would work quite fine.