Sit & Spinner

Real Life Examples: Gold Digger, Mjölnir Game Examples: Arc Pounder

A thwacker is basically a wide chassis with powerful motors (use HP Z-teks if possible) and reasonably big wheels. You then add a long extender going off the rear of the robot and put your main weapon on it (several would be wiser). You can also put another main weapon going off the front.

The tactic of this bot is to "sit-and-spin" (another name for a thwacker), storing as much kinetic energy as it can into his weapon, awaiting for the other bot to come.

Trinity Thwacker

For more power, swap the extender with a long pneumatic piston (you don't need an air tank) and fire it when spinning. If you spin fast enough, the pistons's axle will actually come out of the piston. This will increase the thwacker's range and damage.

A good example of this design, built by Clickbeetle: