Please, please, please know that I don't condone animal cruelty of any kind, and I do not support animal sacrifice! I cannot stress that enough!
I work with animals and their components (blood, bone, claws, and teeth) for magical rites and spells. All parts are obtained humanely. I gather them from the forest (after the animals' soul has passed back into the Earth's embrace, either from old age or the law of Natural Selection), during hunting season (no part of animals taken during this time are allowed to waste) or from the local butcher shops.
With this, we will veer into the area of sympathetic magic. In this type of magic, the actions you take represent the outcome that you want your spell to have. So the heart of a cow is no longer a cows heart, but has become your heart or the heart of the individual that you're either working the spell for or on.
Hearts -Hearts can be used to heal or to harm. Cow or chicken hearts are both easy to find, but cow hearts work better because of their size. They're a lot easier to fit other spell ingredients into.
Broken Heart/Heartache -If you suffer from a broken heart, fill a cows heart full of soothing and healing herbs. Focus on the heart taking away your pain. This heart is now the vehicle by which you rid yourself of your heartache. Pour all of your sadness and pain into this heart. When you feel that you're ready, allow yourself to calm. Take the heart and bury it far away from your house.
Hearts that Harm -If someone has done great wrong to you or someone you love, gather together their picture, a scrap of paper with their name on it, cayenne pepper, pins, and broken glass. This heart is now the heart of your enemy. Fill it with the listed items and allow all of your anger toward this individual to well up. Focus on all the wrongs that they have done to you or another, and visualize the items causing them the same pain that they have brought to you or others. Tie the heart up with twine and bury it in the far corner of a graveyard, and allow the spirits, universe (or whatever force you work with) to do their job.
Feathers- Feathers can be used to "sweep" away energies or to help waft incense smoke around an area for smudging ceremonies.
Bones - Can be cast to read future events, or carved and shaped into spirit vessels for totem animals, guides, or familiar spirits. Skulls are wonderful for spirit housing and can be cleansed and prayed over to invite familiar and totem spirits to your space.
Antlers- Antlers can be rattled together during rituals for calling spirits to you or sending things away from you. The rhythmic rattling can also be used to help lull you into a trance.
Claws/Teeth/Feet -Claws and teeth can tear and rend, but they can also protect. Bless and wear them as amulets of protection or use them in rituals and spells to tear at the image of your enemy or to pierce a poppet made in their image. You can also tie pictures and personal belongings to the feet and bury them to 'trip up' anyone working against you.
Tongues -Fill a beef tongue with herbs and the image of your intended target, and tie it up with twine to silence wagging tongues or those seeking to spread gossip.