Blade is a sumo robot that I have built for BrickFest 2004.
It uses 4 motors with Mars Rover wheels, 2 light sensors sharing 1 input port for edge detection and 2 light sensors for a Dual LIDAR system for enemy detection.
The Dual LIDAR system works like this: The RCX sends an IR message and the 2 light sensors as fast as possible sample the light reflections and then compare them, updating a variable with the highest value. Then it compares left-right values and update another variable. The main loop looks for values bigger than the threshold, makes left-right corrections and when the value get's bigger than a second threshold goes to attack.
For the edge detection I have selected 2 out of my 6 light sensors that have the greatest value differences for the same color. When I connected them on the same input port, I had a 58 value for both on black, 60 for left on white, 62 for right on white and 72 for both on white. Pretty cool, huh?