The heat of a pepper is measured in Scoville Heat Units (SHU), and the hottest peppers in the world are ranked based on their SHU rating. Here are some of the hottest peppers in the world:

1. Carolina Reaper - This pepper has an average SHU of 1.6 million and is currently the world's hottest pepper.

2. Trinidad Moruga Scorpion - This pepper has an average SHU of around 1.2 million and was previously considered the world's hottest pepper.

3. 7 Pot Douglah - This pepper has an average SHU of around 1.8 million and is known for its chocolatey flavor.

4. Naga Viper - This pepper has an average SHU of around 1.3 million and is a cross between the Trinidad Moruga Scorpion, Naga Morich, and Ghost Pepper.

5. Ghost Pepper (Bhut Jolokia) - This pepper has an average SHU of around 1 million and was once considered the world's hottest pepper.

It's important to note that eating extremely hot peppers can cause severe discomfort, including burning sensations in the mouth and throat, sweating, and even vomiting. It's best to consume them in moderation and with caution.