Lulav - the Old-New Jewish Symbol?
Since the state of Israel has effectively taken over the two most common Jewish symbols - the Star of David on its flag, and the Menorah on its official seal - maybe there is need for a symbol of Judaism that is independent of the State of Israel. If so, I nominate the lulav - the palm frond used at Sukkoth as part of the "four species."
As the Talmud tells, us the four species represent all the human types together, and the holiday of Sukkoth itself is considered a universal holiday, since it is a thanksgiving for the past year's harvest as well as a prayer for rain for the coming years. And rain, as the rabbis point out, falls on all people: Jews and non-Jews alike. In temple times 70 bulls where offered as sacrifices on Sukkoth - symbolizing "the 70 nations of the world." Despite, or perhaps because, of this universal aspect, the lulav was a much beloved symbol of Judaism in the late second temple times and in the century or so afterwards. It appears on many synagogue mosaics from that period, and on various coins issued by Jewish authorities.