My first job (unofficial) was working with a chili business so I spent a lot of time working and living around some really hot stuff.
The hottest chili I've eaten was a Bhut Jolokia, at the time the hottest chili in the world rated over 1 mill scoville units and the hottest combined chili extract I've eaten was just over 3 million, though I only had a tiny bit of that as to not die.
For a bit of reference, my dad sampled one of our sauces at a chili festival and ended up in an ambulance.
I still have a bhut jolokia plant growing in my garden, though it's definitely one of the less used chilies in there.