the tanto(as i understand it) is a shorter, dagger sized version of the wakazashi and katana, ie, slightly curved, one sided...etc. the most common ninja weapon was, in fact, the kama(one handed mini scythe for cutting rice) as the ninja, were stealth fighters who were mostly peasants by day, when peasants were forbidden to carry weapons. So, they used tools, or hid swords in walking sticks, and other neat tricks.
Jessyn