It’s not a knuckle that can show your strength, but if you need some necessary tools, Knuckler, the knuckle shaped multi-tool should be nice solution.
The Knuckler is a practical, solid multi tool that measures 2.5 x 2.5 x 0.16 inches. As we can see from the images, the multi-tool features ultra portable and slim design, and looks like a mini knuckle, of course, you can use it a weapon for self-defense, but the knuckle shaped multi-tool comes with over 10 tools, including 1.5″ ruler, scraper, bottle opener, can opener, twist cap opener, hex wrenches, seatbelt or hook cutter, and protractor as well wire stripper in order to help you to deal with various situations, apart from that, the multi-tool is made of stainless steel for solid construction, and using its two keychain holes you can also easily attach the multi-tool to your keychain, keeping it with you.
At present the team of Knuckler is raising fund at Kickstarter. Pledging $16 will let you own the multi tool. If you’re interested, jump to Kickstarter official site for more details.