This article dates back almost a month ago as it was published during the Computex 2015 aftermath. It is therefore very understandable that yours truly missed it and forgot to news it on the front page (even if the boss doesn't think so). In the article appropriately titled Thermal Paste Roundup 2015 – 47 Products Tested", Der8auer has a go at 47 different thermal pastes available on the market. The test subjects range from the Akasa 455 to Zalman ZM-STG2, and yes ... that's in alphabetical order.
The test itself is very inclusive with a detailed description of the methodology. On Air Cooling we see a good recommendation for the liquid metal based Phobya LM if you're looking for pure performance and the Cooler Master IC Essential E1 if you're aiming for the best bang for your buck (or Euro, or Yen, etc). For the extreme overclocking part the Gelid GC-Extreme finally sees competition after a 6-year reign in the form of Kryonaut by Thermal Grizzly.
I recommend anyone checking out the article at Overclocking.guide to learn more about the behavior of the different thermal pastes. In particular the Product Description table is nicely detailed with all the information you need to make an informed decision.
Oh, and before I forget! Der8auer also made a video explaining the different methods of applying thermal paste. You know - so you don't mess up your system cooling after buying awesome cooling paste. The video is linked to the image on your left-hand side (possibly on top if you're browsing mobile).