They open and close to fit into a variety of nooks and crannies, and as a result have become perhaps the most popular piece of rock equipment. Your wallet also will be a constraining factor. Unlike nuts, cams are pricey. Snow and ice protection. The basic options for protecting yourself on snow and ice are pickets, flukes, and screws.
Ice screws are a more serious tool.
Ice is tough stuff, and so are these screws, but placement problems and the uneven quality of ice make climbing on ice a dicey proposition. But well-placed screws can offer a solid measure of protection. Of course, if you're on terrain where you're driving ice screws, you might want an ice hammmer as well. One other piece of equipment that might come in useful on hard stuff is an ascender. An early photo.