With a heat range from 1.4 to 2.2 million Scoville heat units, the Reaper sits atop the pepper scale. It's currently the official world record holder.
With near equal heat to the Reaper (1.4 million to 2.2 million SHU), the Komodo Dragon hits very hard.
Another chili with vicious bite, the Scorpion pepper ranges from 1.2 million to 2 million Scoville heat units.
The 7 Pot Douglah has a wide range, from 900,000 to 1.8 million Scoville heat units. As a "chocolate" chili, it has a beautiful brown hue.
The Dorset Naga ranges from 1 million to 1.6 million SHU. It's a sub-species of another super-hot - the Naga Morich.