NanoRover

Perhaps the smallest and cheapest rover you can print.
The stepper motors are 4 Wire 2 Phase Mimi stepper motor micro stepper motor D6xH11mm with small Copper gear: http://www.amazon.com/gp/product/B00M7QQIZ6?
Found this datasheet online: http://www.nidec-copal-electronics.com/e/product/files/file/b862724e290bcc90376e42235e959fd090c36ad7.pdf
Seems it can pull around 300mA for 3N so try to get better batteries that what I have. I suggest two 3.7V 680mAh lipo batteries tied in series to the Raw pin on the arduino. Here's what I plan on upgrading to: https://www.amazon.com/gp/product/B00MF3SAF2/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A3EFY0HU0G8BT6

The controller is Estone New Version Pro Mini Module Atmega328 5v 16m for Arduino Compatible: http://www.amazon.com/gp/product/B00GLES8BW?

After the 8 DIO required for the steppers, you are left with 6 DIO and 8 AIO for any sensing you want to add to it. Keep the batteries light since the steppers cannot handle too muc