I use paint shop pro 12. It's pricey but its way more anvanced and works with multi layers etc. If you want simplicity go with the gimp app. If you have skills in image editing or really want to fully create your own icons from scratch or even edit existing icons then go for a more advanced image editing software that can export a multitude of image formats with multi transparencies etc. like paint shop pro. To each his own, shop around on the net. Good luck.
