A great Hat mic is the SM7B. It captures the hats without as much hi frequency as the oh's, allowing you to "place" them in the stereo field with greater ease and less "smearing" than a 451 or sm81.
I don't usually need a hat mic to adjust the volume, it's usually blasting through the overheads. That is why I like the SM7B. It allows me to place the hats in the stereo field when the drummer is bashing the hats way to hard.
It is also great for vocals!