Obstacle Course
Essentially a mix between board the platforms, multi-man, break the targets, and various story mode levels throughout the series and Smash Run.
You start out on a platform similar to Home-Run Contest and just start running, as you run you'll pass various obstacles that you have to jump over, roll under, etc, there will be platforms that activate mechanisms that open up the path at various points, and targets that you hit to regain health, all while being bombarded by various enemies.
I imagine the course being randomly generated and infinite, when you die it ends and your score is tallied based on the distance you reached, number of targets you hit, number of platforms you activated, number of enemies you defeated, and amount of damage you dealt.