Mobile robot on rough terrain?
814029
a hexapodal robot with six legs, they are very stable, and act like spiders, and the algoritms for their motion are quite easy. but not quite as easy as just wheels.
946923
auto vision systems and autonomous vehicles
1116467
I am not sure how cheap you are looking for, but here is s start.\n\nhttp://www.hobbytron.com/RobotArmKits.html
371906
that is actually a good idea!  now, where can we find a robot?
903289
u may built remote controlled toy. but as for the robots that is a tougher job. u may browse this site  http://www.robotics.com/robots.html
134377
Self Guided Vehicle or\nSan Gabriel Valley or \nSchweizerischer Gewerbeverband
432769
Consider iRobot. They build robots for the Department of Defense and also the robot vacuum cleaner.\n\nhttp://www.irobot.com/
824660
resources are just that...resources...you find them anywhere...hardware stores...in this case maybe marine/scuba stores...grainger sells electric motors for battlebot builders...
598895
Motocross is the most likely.\n\nThen again, body armour would come in quite useful for geocaching when the GPS is indicating that the cache is in the middle of a gorse bush or something similar.
256564
Creates a lot of motion but doesn't take you anywhere?
271525
You should try reading "Flesh and Machines" by Rodney Brooks.  He does a nice cursory overview of the history of robotics and the implications on society of their existence.
268576
Robots have a very important application in situations where human beings have a life or health risk- like handling bio hazards, radio active materials, extreme temperatures or vacuum, or distant places like mars where it is easier and more economical to use machines like robots to things with remote control. They are also used in production line like automobile industry to assemble, weld, fix etc, becuase they can do the same action hundreds of times with high accuracy without getting tired.
86601
Hmmm... Right now, i'm sick of traffic jam, so if I were a product dev. manager, and I can make anything I want, then I'll make a TELEPORT MACHINE: A Machine that can move you to anywhere you want in just seconds!! (You know, like those in Star-Trek or other science fiction movies..) I'm sure it'll be very, very usefull in our life, especially in BIG CITIES!!!Also, it'll lessen the air polution and much more efficient!! ^---^
1077879
Rollercoasters are more in the Mechanical Engineer's realm.  Robots are a joint effort between ME's and EE's, usually with the help of a programmer.
78308
Real World/Road Rules Challenges
102498
You are reffering to the Mars Exploration Rovers.  There is also a probe on it's way to Mars to see if it had any long standing bodies of water.
689568
Try using an airplane, a navigational wheel, or something along those lines.