This is my RoboKiller that I used in a little remote controlled robot battle contest with a friend of mine.
Unfortunately I build all of the weapon system the night before the contest, just finishing the pneumatic system 3 hours before the start of the contest and I was VERY tired! So tired that I only cared to test the lifting mechanism of the arm/scoop which worked with 4 pneumatic cylinders. It worked, I jumped to bed, slept for 2 hours, woke up and rushed to the contest place. 
On arrival, I first tested the driving... But the robot was to heavy for the low torque/high speed gearing Iīd build, so the ībot didnīt go anywhere... DAMN!!! 
To make a long story short, I didnīt have the time to rebuild the robot, correcting my gearing errors, so instead I ripped it for scoop, lifting arm, counterweight, compressor and motorized pneumatic switch, leaving the robot in the condition seen in the photo at "@cj versus Revi".
My emergency plan was to drive @cj robot off the battlefield, hitting it with high speed impacts, but @cj's little high torque/low speed was, of course, much stronger and won 3/3 battles :( 
Lesson is: ALLWAYS TEST PROPERLY!!!! 
...and in pushing contest like this, torque rules over speed, at least with my poor driving skills...

The RoboKiller(NOT!) used 1 rotation sensor for the pneumatic switch and 2 RCX'es, but one could have done the job...
The remote control used 3 touch and 3 light sensors, worked great, but broke to easy... there was 3 in all, 2 heats in each.