10/13/2020 update: Cheat developers started using the Interception driver for malicious purposes, and some services (FaceIt, Vanguard) have taken issue with players who have the Interception driver installed. Fortunately, a few developers in the gaming community have taken it upon themselves to create a standalone mouse acceleration driver that can't be abused for cheat purposes. The new version of mouse acceleration that I personally am using can be found at the following links.
Original (outdated) post is below, but I highly recommend using raw accel.
In late 2015, Povohat and I proudly released the interception-based mouse accel driver. It provides users with the ability to use mouse accel similar to the features that were available in QuakeLive, but across their entire OS and in any game.
In May 2019, FaceIt started blocking the interception driver from being used with their anticheat client. They claim they have seen cheats that use the driver, and they haven't been open to the possibility of whitelisting this particular use of the driver. Please be aware that you should NOT install the interception driver if you play games such as CSGO using the FaceIt client.
In May 2020, Riot's Vanguard anticheat (for Valorant) also started blocking the interception driver. About a week later, they unblocked the driver, so all should be well again with Vanguard/Valorant.
- N.R.K created a GDoc that is a compilation of resources/information available for the driver, and it is an excellent place to go if you have any questions.
- Before this site, I had all of the information I made publicly available on http://mouseaccel.blogspot.com. I still recommend you go to N.R.K's guide first.