I can't believe I'm the only one that uses aseprite! Completely free but with all the attractive features of paid pixel art programs (layers and opacity, animation, magic wand and more) and it still has the eraser trick! I've tried GraphicsGale and others (and I don't like doing pixel art in traditionally graphics-focused programs like GIMP and Photoshop) but aseprite was the one that convinced me to graduate from good ol' Paint.