Some chemicals certainly have extraordinary properties. One can consider them extreme in a sense, that they are the prime example for a concept, or they achieve the highest or lowest values in a certain area.
This Q&A attempts to compile a list of questions asked on this network, which have a background related to such extreme values or properties. we decided to add such a list because it is a popular search term.
It is a community effort, hence everybody with more than 100 reputation points can edit the answer. If you think something is missing in this list, just go ahead and add it. This post will be locked to prevent adding new answers, though. The corresponding discussion can be found on meta.chemistry.se. If you think there are some obvious points missing here, please go there and open a discussion.