Hmmm. Polonium is very radioactive and toxic, and was used in dart form by soviet assassins. Effect is instant and only takes ten micro grams... Lead and mercury cause insanity Bismuth causes the gums to turn black in huge doses but is not fatal Thallium is VERY hard to trace since the side effects are really generic Cesium explodes instantly on contact with water or skin Selenium is toxic (don't know what it doss though) And arsenic is god damn arsenic. What is your favorite? My answer is fluorine. Because it is SO REACTIVE. [spoiler]lol jk furry's are perfectly fine.[/spoiler]