Waluigi. He's just a Wario ripoff. He also looks like he's on crack. I bet a gust of wind could knock him down. I also bet everyone $1.00 that he doesn't appear in another game. I'm not a fan of Peach either. She's so blinded by Mario's success that she dousn't really care about Luigi, Toad, Yoshi, and even Wario(He found the golden statue of Peach but Mario stole it).
Note to Ultra Metal Luigi: I know my name's Ultra Luigi, but I am not copying you. I never heard of you until I read your opinion about this topic.