Sometimes you can turn it on by holding Command, Control and Power button. more than 3 seconds. The Power button replaces the Eject key in the case of the MacBook Air and the MacBook Pro with Retina display
Another method is to unplugging the battery connector for a few minutes, reconnect it, then connect the charger. OR short out pins 3 and 9 on the keyboard to logic board connector.
Of course you realize you could damage the board with this method.
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