The first interesting component I found was a Geiger counter that is available as a component for Arduinos.
It is used to detect radiation levels dependably and is suggested to be kept in an enclosure due to the high amounts of voltage going through the circuits. It is only really useful if you need to be sure there is not a dangerous amount of radiation near you and would probably only be used in a laboratory that deals with radioactive materials. https://www.sparkfun.com/products/11345
The next interesting component I found was a RGB and hand gesture component that allows for ambient light but also senses hand movements. It can sense 6 hand motions, near, far, left, right, up, and down and more can be coded for it.
It can be used to determine what a program is supposed to do by the hand gesture you give it. It can be very practical when getting lights to turn on or off by just the simple swipe of a hand. https://www.sparkfun.com/products/12787
The third interesting component I found was a triple axis magnetometer. It allows for the accurate measurement of the current compass heading.
It could be used to get a program to display the current heading of the sensor on the object to show the direction. https://www.sparkfun.com/products/12670