Reimu's ofuda. These paper talismans are not only for bullets―Reimu uses them for exterminating youkai and exorcising phantoms too. She is fairly unsparing with them, letting Rinnosuke use them for free and sticking them all over the temple school.
Reimu always throws her ofuda at people before making any decisions. If they are normal humans, the ofuda will not have any effect on them, but they can be quite troublesome for youkai in disguise.
Ofuda might not be effective on youkai children who have little youkai power or lack direct contact with humans. When a young bake-gitsune, or youkai fox, showed up at the temple school in the past, it made fun of Reimu because her ofuda had no effect on it.
Reimu uses both ofuda and needles when she attacks depending on which she thinks will be more effective. Ofuda, which are made out of paper, are probably not that useful against those who can use fire...
Whenever Reimu hears that a Seal Crystal has been found, she will rush straight to it. She has always been quick to respond to incidents with her trusty ofuda by her side.