The Sikh bracelet makes a devastating knuckle duster that is always with you; a flip of the hand can make it rest round the top of the hand to strike with.
and "but officer I'm just wearing a bangle; you mean people actually use these as weapons?"

from Wikipedia:
Iron Fist Fighting, also known as Loh Mushti in Northern India (Punjab) is the traditional Sikh form of boxing. Instead of using gloves, the Sikhs would use their steel or iron bracelets, known as karas, which came in many sizes and forms including battle designs with sharp edges or spikes. Iron fist fighting can result in death.

qjs