Lucky Guess

 is a secret achievement/trophy in Deus Ex: Human Revolution. It is earned by entering the code "0000" onto the bomb's keypad during the side quest Smash the State. Alternatively, any means of disabling it except hacking will also earn this achievement.

Walkthrough
After learning of Sandoval's location, the side quest Smash the State will start when you bump into Officer Nicholas in the convention's entry area. Proceed with the quest and, when you discover where Jacob White is, you see he also has a bomb. Merely put in the code "0000" to disarm the bomb (hacking it will NOT earn you the achievement).

Other methods

 * use an Automatic Unlocking Device
 * Using the Icarus Landing System, climb the ladder next to the bomb and perform a stun to disable it
 * use a gas grenade