Sentry guns are basically weapons that can automatically aim and fire at a target. While that may sound intimidating, building one yourself is easier than you think, should the tools and supplies be at your disposal. Continue reading to see three amazing homemade examples.

3. Paintball Sentry Gun

What do you get when you combine a paintball gun, laptop, and custom software? In this case, an autonomous, self-targeting paintball sentry gun that’s able to shoot down targets without user input. It may not be powerful enough to actually hurt an intruder, but they’ll be startled nonetheless.

2. Airsoft Sentry

Built and programmed by Bob Rudolph, this awesome robotic sentry gun was designed to locate intruders, determine their path, and then fire at them. In other words, “the sentry gun picks up its target using a webcam attached to its tripod, which a laptop translates into movements for the servo motor controlled gun; once the target is in range, it’s blammo from gun pelting you with paintballs or AirSoft pellets.”

1. Nerf Sentry

Modder Rick Prescott converted a standard Nerf Vulcan EBF-25TM into an autonomous, heat-seeking sentry gun for MAKE’s weird gadget contest. Technically speaking, “Prescott paired a Nerf Vulcan machinge gun with some Devantech TPA81 thermo sensors and a ATmega168 microcontroller.” That’s not all, he says he has “grand plans to deploy the infrared seeking sentinel facing the entrance of my work cubical in order to speed interaction with less desirable visitors.”

Honorable Mention – TF2 Sentry Pod

Special effects masters WETA Workshop of District 9 fame have built a life-sized Team Fortress 2 level 1 sentry pod that not only looks cool, but also features motion-tracking and even authentic game sounds.