Not to sound elementary, but for the letter A, I'm starting with apple. I use them quite a bit in my practice. Cut an apple horizontally, and they have a little star or pentacle in the center. They embody the maiden, mother and crone with their colors-- red skin, white inner flesh, black seeds. I think of apples as a sacred food.
I associate apples with the Autumn Equinox and with Samhain. Around September, apples are ready to be harvested and I've used them along with grapes and nuts to decorate my Mabon altar. Since they're also considered food for the dead, I leave an apple out for passing spirits each Samhain.
I've collected many different pieces of wood for wands over the years, but the one I've worked with the most is a beautiful piece of apple wood. I've cut it down to a nice length and done some peeling of bark and sanding. I still want to do more with it, adding the ogham letter for apple and some other symbols and perhaps carving some apples on it (not sure if I'm talented enough for that). But even unfinished, my apple wand feels very magical.
Are apples important to your practice of the Craft?