The NavX2 IMU Robotics Navigation Sensor (navX2-Micro) is a great sensor for orientation in competitive robots. The navX2-Micro is a second-generation 9-axis inertial/magnetic sensor and motion processor. 

The NavX2 Micro IMU, (Inertial Measurement Unit), Robotics Navigation Sensor, is a great small footprint sensor for precise robot orientation in competitive robotics challenges. The navX2-Micro is a second-generation 9-axis inertial measurement unit magnetic sensor and motion processor. Designed for plug-n-play installation onto robots such as those used in the WorldSkills Robotics Compentitions, FIRST Technology Challenge (FTC) and the FIRST Robotics Challenge (FRC), the navX2-Micro helps you Build Better Robots by adding sophisticated navigation capabilities to your robot builds.
 

IMPORTANT NOTE:  To avoid having the navX2-Micro reset due to a RoboRIO brownout, connecting the navX-Micro to the RoboRIO via USB is highly recommended.