Thanks everybody for the feedback. With much thought and considering the poll and your replies, I'm going with a Head Knife. I think it says "leather work" more so than a mallet. I decided to shy away from a mallet because... well... there's already an ARM and HAMMER company out there:
That said, here is the logo I've bee producing for myself. I will get this made into a stamp as well. The ARM is my initials, I am left handed, do all my work by hand, and I love medieval/celtic/heraldry styling in my work so I think the mark kind of says all of these things.
Thanks again.
-Andy