There are 6 guns to chose from (by using the track-pad on either controller):
Pistol (Swipe up. It is the default gun) - has a laser sight and deals instant damage
Pulse Laser (Swipe diagonally, upper right) - firing rate slows down over time. You can keep it from overheating by watching the meter at the end of the gun.
Shotgun (Swipe diagonally, lower right) - deals high amount of damage at close range.
Rail Gun (Swipe down) - will need to be charged before a shot can go off. You can monitor the charge status by watching the meter at the end of the gun.
Laser Beam (Swipe diagonally, lower left) - will shut off once it overheats. You can monitor the heat level by watching the meter at the end of the gun. You can also cross the beams from two guns to triple its damage.
Grenade Launcher (Swipe diagonally, upper left) - pulling the trigger once launches a grenade. Pulling the trigger the second time detonates it.
You can switch out a gun for either a shield or tractor beam by reaching over the shoulder.
With the shield, you can press trigger to activate a pulse that pushes the drones back and deviate lasers. Also, you can hold the shield side ways to provide maximum horizontal coverage.
To use the tractor beam, you point the top of it at a drone and press trigger to activate it. You can then slam the drone to the ground to damage or destory it. There's a small strip on the front that can be used to deflect lasers.
On the ground in front of you, you can see a radar that shows the positions of the drones. It helps you locate drone that are out of your immediate field of view.