Neural-inhibitor collar
From Halopedia, the Halo wiki
Neural-Inhibitor Collars are thick bands of metal that, when placed around the neck, stop any neural signals that aren't necessary for continuation of life, utterly paralyzing the subject. The UNSC tried them for capture of dangerous felons but the technology was put aside for an unknown reason, but most likely for safety reasons.
General Graves used them when he tried to capture the Spartan-II unit "Blue Team".[1]
