Since his first appearance in the whole Mario series was Mario Tennis on N64, you know you have to have Waluigi in any Mario Tennis game. He's still trying to make a real appearance in Super Smash Bros.
He's a defensive character which theoretically gives him the best range.
I honestly didn't think that was more or less true than some of the other characters.
But overall I liked him, but he wasn't my favorite character in the game. Didn't play a lot of matches with him, when all was said and done.