Smaller robots can be really fun. Here's a 1lb combat bot I'm making for the RoboNexus expo in October.
It uses 60:1 copal gearmotors ran at 14.8v off of two LiPoly packs in series, and a micro reciever from
The Robot Marketplace
The speed control is an Ant-100 from
Barello.net
The chassis is a milled block of UHMW
The tires are from a local
Slotcar Track
Beyond that, all you need is a transmitter(75mhz, normally) and it's ready to go.
Note: this was milled on a mill from harborfrieght, and all the dimensions were figured out on the spot, so it is a bit sloppy, but perfectly fine for it's purpose