Lauren Bacall or Sigourney Weaver, to reference two different eras. Bacall with Bogart, and Weaver's orchestra musician character in Ghostbusters.
Tall (I still want to be able to reach the top shelves), assertive without being aggressive, mature woman's voice (Bacall even as a teenager), willowy, classy, confident-yet-vulnerable, just the right amount of sultry.
Sorry, but the modern-media flossy-bimbo look just doesn't impress me.