Microplane makes the very best graters for spices, citrus zests, chocolate and other such things. They are the sharpest, easiest to use, and most durable grater of this type that we've come across.
The Professional Series Fine Grater is the perfect kitchen tool for grating a variety of hard spices like cinnamon, dried ginger and turmeric pieces, and nutmeg. It's also excellent for citrus peel, fresh ginger, parmesan cheese and almost anything else. It can be paired with the Slider Attachment for grating several nutmegs or other pebble-sized spices at once. It's dishwasher-safe and has a full stainless steel handle.