The Armenian Ark coins are interesting if you look for smaller sizes at a decent price. There are several other silver coins that come also in smaller sizes than 1 oz, but usually the price per gram sky rockets the smaller they are. It comes from the minting cost and the dealers margin.
I found that the Ark coins had the best value in that respect. So especially for preppers that is a interesting coin group, if you intend to use it for bartering and look for smaller pieces than 1oz.