I present my mini sumo robot "Destroyer 3000"

Parts:
Aluminum body;
2 aluminum wheels with casted PU tires;
3 cell LiPo 0.8Ah battery

Mechanical:
2x 12V 1000RPM motors;
2x Pairs of 1:2 Bevel gears;

Electronics:
1x Arduino Nano v3.0;
2x Freescale MC33877 drivers;

Sensors:
1x TSOP31236 IR receiver;
4x SHARP 340K 40cm proximity sensors;
2x TCRT1000 Line sensors;
2x Overfall detection microswitchs;

More tech. stuff in destroyer3000.blogspot.com