Robotics Expert (Fallout 3)

Robotics Expert is a Fallout 3, Fallout: New Vegas and Fallout 4 perk.

Effects
Grants an extra 25% damage dealt to robots. Also, entering sneak mode and activating a robot permanently shuts it down.

Fallout 4
Though not mentioned in the perk itself, to be able to hack a robot requires approaching a non-hostile robot or sneaking undetected up to a hostile robot. As such, investment in sneaking may be needed if you want much mileage out of this perk.

When you power off a robot, you can still initiate a self-destruct by re-hacking the robot.

Initiating a self-destruct will take some time; moreover, the simple act of initiating self-destruct will do a small amount of rad damage to your player character.

Legendary Protectrons have a significant secondary detonation upon being self-destructed and requires the player character to essentially flee to a safe distance to avoid being killed.

Additional dialogue
Additional dialogue options are unlocked with certain robots with this perk. These often bypass Speech checks:
 * You can program Dean Dewey to let you pass.
 * You can disable Cerberus's combat inhibitor causing him to attack the ghouls and yourself in Underworld.
 * You can force Button Gwinnett to shut down, allowing you to grab the Declaration of Independence.
 * You can program Milo in the Nuka-Cola plant to think you are an employee.
 * You can bypass the RobCo facility section of the Wasteland Survival Guide quest while getting full credit for the job.
 * You can reprogram the mainframe in the mobile base crawler to have the security robots attack the Enclave instead of you. There is an additional dialogue with Stiggs where he tells you about this when you first enter the room.