Back in 2013 I was part of DROID, an intelligent robotics team at the University of Brasília. The challenge for that year was a robotic volleyball: Each team was allowed 2 robots in the arena and their goal is to keep all the blue balls in their side of the arena (because they count positive points) and to throw the orange ones to the other side of the arena, reducing the number of points of the other team. It is a bit hard to explain through words, so take a look at a video:
One major challenge was stabilising the value received from the physical sensors attached to the robot in a competitive setting, where there usually is a lot of light sources and noise. Loud music around the challenge arenas was one of our main issues. I figured out that we needed to develop a low-passing filter in order to filter audio and allow our sensors to be useful again. It worked, and we ended up winning the 1st place against at least a dozen teams coming from the best universities in the country.