Which are the best free data visualization tools available in the market?

It’s said that the new currency of the world is data, and the exchange unit is web through which it's dealt. As customers, we're certainly swaying in data, it's all over the place from tags on food packing design to World Health Organization reports. As a consequence, for the designer it's becoming gradually tough to present data in a way that stances out from the frame of challenging data streams. Can guys suggest some best data visualization tools?