For the 2003 Autonomous Robot Contest, we designed and implemented a robot with a big claw. Not only would this instrument be used to detect the robot's position and orientation as well as the position of the balls and cup, it would also raise or lower itself and open & close to pick up the balls and drop them in the appropriate places to score points.
Our planned strategy was to climb up the hill and pick up a ball of our team's color, travel to the bottom of the hill, and place the ball in the cup for a score of 4 points. If our opponents' ball was already in the cup, our claw would take it out, and put our own ball in. We placed photo sensors on the front and bottom of our robot so it could linefollow and distinguish between the different colored balls.
The robot, once completed, looked beautiful. The only problem was it was unable to do anything. Hours before the qualifying rounds, it managed to linefollow up the hill and attempt to grab a ball. In the actual contest, however, it lost miserably to a team which scored 4 points and received a standing ovation. That was the last time our robot would compete.
The day before second rounds, our robot lost all its strength and could no longer travel up the hill. This was probably due to burnt chips in the handyboard. It was a sad day, but at least everyone could go home and sleep =)