AndroidJoystickTest.apk is a simple app (hacked together from Google's ApiDemos example) which plots analog stick values from a joystick on a graph. Just launch the app and wiggle the joystick around for a while. Using this you can see if a joystick has "dead zones": areas where values are remapped to zero. These will show up as higher concentrations of red dots. These dead zones are generally included in firmware to prevent drift by ensuring values are zero when the joystick is released, but they can inhibit precise motion, making it harder to aim accurately as a sniper in a fps game, etc. You'll see that the PS3 and XBox 360 controllers have no dead zones.