Currently I use a scorpion 4035 motor. These come in a number of KV ratings and tbh I can't remember which I have in boner as it's rubbed off. This motor is an outrunner, ie the magnets in the outer can rotate along with the shaft whilst the copper coils in the center remain static.

Inrunners as the name suggests rotate internally with the magnets sitting in the center of the motor.

For a given voltage generally an outrunner will spin slower than an inrunner. You will also get more torque from an outrunner than an inrunner (generally). These both mean that an outrunner is usually better for combat robots as they require less gearing to get a useful rpm range for a disc or drum.

The power of the motor will be given in the specification. The 4035s give around the 4 to 5hp range (same as a big magmotor!) and peak even higher.

The controller i'm using atm is a Castle Creations Phoenix Ice 2 160HV ESC. A very nice controller that has a data logging feature that means that i can download the data from the controller after the fight and see the current draw, voltage, temperature and rpm of the motor during the fight.