Non-Gecko (Firefox), non-Blink (Chromium) and non-Webkit (Safari) browsers:
Servo (browser engine)
https://servo.org/
Ladybird
https://ladybird.org/
They don't seem ready for use yet though.
Firefox, Chromium or Webkit? We will have new choices soon: Ladybird and Servo
@jikomayo worth noting that Servo isn’t a browser, but rather an engine to be used by a browser
@dan Thank you for correcting me
@jikomayo am looking forward to Servo really.
Internet Explorer
https://www.microsoft.com/en-us/download/details.aspx?id=41628