It does not have to be a snow pile (but they are fun throwing ^^) you can use any item that gives you a target cursor. Like a dagger for example. But I assume you are on Siege, and then you want something blessed. Snow ball, cream pie, dye tub, valentines card or whatever. There are numerous things you can use. There is also the option of using the skill arms lore to target, but that gives you a short timer until you can steal. I've also heard about people using the honor virtue, but I have never tried that myself.