Knitter's Pride is one of the few products I personally refuse to buy. They're Knitpicks Options clones.They skirt the copyright laws by alternating the colors differently. I don't think it's ethical. I always get rebuttals from the moderators refuting this, but I got it straight from Knitpicks' customer service reps in a reply email to my inquiry about it.
My other product is IAMS pet food. They contract with a private lab that does cruel animal testing. I WILL NOT support that. I don't boycott too often, but when I do I have a strong conviction about it.