I'm going to have to go with Shar.

Simple, elegant, with subtle beauty, deep mystery, but an unmistakable aura of menace.

It's a symbol that can be used in clothing and architecture without looking overdone, and also does a fantastic job at representing a night goddess that opposes a moon goddesss, as well as her being a goddess of loss, secrets, and forgetfulness. It even is in the form of her favored weapon, the Chakram.

One interesting aspect of the physical holy symbols is that the material that they're made from is of extreme significance. Though the design never varies, whether the central part is made of common stone or ebony, onyx, or jet of deep significance, just as whether the border is made of purple quartz, amethyst, or even purple sapphire, signifying rank within the strict hierarchy of her church.