Piracy on the high seas is a growing problem, so the Navy's latest lightweight fighter, the Littoral Combat ship, has a system specially designed to knock out pirates without killing them (so it obviously don't use ninjas). The Running-Gear Entanglement System, developed by the Coast Guard, is decidedly low-tech—basically a floating net that jams up smaller boats' propellers, leaving them stranded if they breach the perimeter, and easy targets for boarding.
Unfortunately, as Jesus points out, the dangling, 40-inch nylon loops that do the ensnaring don't exactly sound animal-friendly, especially if they get tangled and twisted. Unlike ninjas, who would kill pirates, and only pirates, with absolute precision. The Navy should look in to getting some. [Danger Room]