[aaronweiss74]

I'm going to have to agree with all those who said that programming the drive system really isn't difficult at all. The most common systems are ready-made and quite frankly, there's absolutely no good reason other than elitist-ness to rewrite them. If you take programming in FIRST as an opportunity to prepare for programming in the real world, you'll have to realize that you get paid to produce new work, not rewrite already working code. As the old saying goes, don't fix what isn't broken. As for an actual answer, it has to be something complex to the point where you require advanced math, many motors, and coordination of such motors. Or something like what's already been mentioned where you switch between some or many drive systems. Walkers, tripods, and things of that sort will always be more difficult than a wheel system though.