Starting in 2015, Gazebo has been included in the kit-of-parts delivered to FIRST teams. FIRST is a robotics competition held annually where high school teams build a robot to solve a unique challenge. This year's challenge is called Stronghold. A team's robot must breach an opponent's defenses, and weaken and scale their tower.
Gazebo is used by teams to experiment with robot architectures, test designs, and practice competing. Teams have access to a simulation environment that matches the 2016 game field specifications. Additionally, WPI provides numerous tutorials, interfaces, and support through FRCSim, a FIRST specific simulation environment that builds on top of Gazebo.
Of course you don't have to be a FIRST participant to use Gazebo or the competition environment. Try out Gazebo's new Model Editor to build your own custom robot. Use a joystick to control your robot, or write your own plugin to add extra functionality. Can't find what you're looking for, or need help? Check out out the questions and answers forum at answers.gazebosim.org.
Good luck to all the teams!