Hello,
The Pololu Zumo chassis is great for any custom sumo robot build.
This one features the chassis, blade, reflectance sensors, 1:75 motors, optical encoders with special signal processing, nRF24L01+, Bluetooth, laser sensors and MP3 sounds under a Darth Vader costume:
More technical details: http://mcuoneclipse.com/2014/12/23/darth-vader-santa-claus-sumo-bot/
Happy Vadering
Erich