Razor blade soap is exactly what it sounds like, unless you thought it was razor blade shaped soap, in which case it's not. No, razor blade soap has an actual razor blade inside. A nice rusty one. But don't worry -- you'll bleed out well before the lockjaw sets in. Available for $7/bar, it makes the perfect gift for that special someone in the slammer. Alternatively, Polish roulette!
Razor Blade Soap Puts Your Nipples At Risk [nerdapproved]
Thanks to Closet Nerd, who once made soap with a revolver inside and shot himself in the butt. Use a wash cloth, bro.