One of the things that I really liked about WhatTheKart! is the unique boost mechanic. When you drift, you build up a boost bar. Once the bar is full, you can press the boost trigger to launch your kart forward.
What do you get when you mix Mario Kart with Rocket League?
The prototype called Metamars by BoredElonMusk is the answer. It's a great kart racing game with low-gravity physics that makes for some exhilarating races.