Here is a nice freebie that not only provides basic ninja training, but tests touch-screen precision as well. Training Ninja is an Android game where your only goal is to hit as many targets as you can and post your score online.
The concept is simple. There are 10 rotating tiles in front of you, providing one of the 3 targets available. Hit the regular ones to get points and as long as you avoid hitting the crossed tiles, you up your combo as well. The yellow targets are considered to be lucky. While smaller and harder to hit, they add considerable amount of points when struck by your mighty shurikens.
Training Ninja offers 8 different challenges that you can complete to unlock some of the additional shuriken types. Google leaderboards are supported and you can compete against your friends or the rest of the world.
Seus Tio Studio is a brand new developer and Training Ninja is their first release. I don’t know if this was intentional (or something is broken), but I didn’t notice any ads or IAPs while testing the game. It’s completely free. Give it a shot by following the link below.