One half of the recent [CPU Exploitation desaster](https://meltdownattack.com/).
The paper is not even that complex and in a scientific way keeps repeating itself.
It clearly lays out the simple instruction sequence that's necessary to trigger the exploitable behaviour.
Quite a nice addition to the [explanations by Google's Project Zero](https://googleprojectzero.blogspot.de/2018/01/reading-privileged-memory-with-side.html).