In the past few months, we have covered a bunch of awesome self-defense tools here. As JoergSprave has demonstrated in this video, you can turn cheap IKEA pencils into a weapon. You can use them to build an IKEA pencil switchblade or take the next step and assemble a C96 pencil shooter. The magazine holds up to 10 rounds.
This is not the most dangerous self-defense tool but as JoergSprave has demonstrated over the years, you can pretty much turn anything into a viable weapon.