Waluigi

Waluigi is a tall, fast, and has a double-jump, but takes  way  more damage than other characters. He can also walk up certain slopes that other characters can't. Waluigi's double jump acts as the second jump in a series, meaning when you land and are moving forward when you jump again it will be a triple jump. Note you can also do this extra jump out of wallkicks and into wallkicks as it refreshes on a wallkick or when you hit the ground. Meaning you can Jump>Extra Jump>land>Jump and move forward to triple jump>Extra jump>wallkick to gain height and reset your extra jump>Extra jump. This allows you to get on the castle roof from the side fairly easy.

(This entry made possible by nicemaster12s post on character abilities)