Charlie Stross' Laundry series. Good stuff, and could benefit from a rewrite-with-hindsight.
The Dresden Files, say, appears to be running out of headroom for Dresden to be able to throw down without actually wiping Chicago from the map permanently.
I'd love to see a treatment of the Laundry with a long slow build that turns out to be the ramp to an exponential progression to Case Nightmare Green.