Actually, there are lot of Gems and/or minerals that can be dark red and translucent but easy ones that come to mind are Pyrope, Almandine, some Spessartine and I believe, even some Grossular Garnets! However, there are quite a few more.
If one is referring to the stone being natural color and closely resembles a ruby, then the above stones are within the realm of thinking which can make the common ruby hard to tell if in fact it is a ruby.. But other stones (once heat treated) IE topaz can also assume a ruby's appearance.