Reset your Mac's EFI Extensible Firmware Interface) password

So you're locked out of your mac because a firmware password has been set and you forgot it. Don't worry, there is hope and you have several options:

Firmware Password Utility: 

• Boot from OS X Recovery (Time Machine, USB, internet recovery, etc.) 
• Go to your Utilities Menu and choose Firmware Password Utility to either reset your password or to turn it off. 

Firmware Password Utility

 EFI Reset Tool (I also take no responsibility for any illegal use nor do I condone this). 

• Go here to read about the tool: http://hackaday.com/2013/02/26/mac-efi-pin-lock-brute-force-attack-unsuccessful/. Sometimes this method doesn't work and there is a reason. 

Reset PRAM/NVRAM three times:

• Add or remove a stick of ram. Obviously if you have one stick in, add one and if you have two in remove one. 
• Power on the mac and immediately press and hold command-option-P-R. 
• The system will restart with the ‘bong noise’, allow it to do this 3 times. On the third ‘bong’ you can let go of the keys. 
• The machine will now boot with a cleared password and reset PRAM/NVRAM. 
• You can shut down the machine and replace the original ram configuration. 

Hold in the power button:

• Press the power button for ten seconds until the front indicator flashes. 
• Keep holding the button till the mac starts up; this way your Mac EFI is reset. This will help in a lot of problems. 

If nothing works, I am afraid you will need to go to the Apple store and show proof of purchase before they reset the EFI for free. Here is a little more information on this topic.