Here is a classic knife design from WWI that you can get your hands on for self defense. The WWI 1918 Trench Knife has a 6 3/8″ AUS-6 stainless steel double-edged blade. Its heavy duty handle serves as a skull crusher. The knife measures 11″ in overall length.
Like what you see? You can get one of these for under $20 at this time.