Because Peter David's X-Factor is a consistently enjoyable book and Jamie Madrox is one of my favourite mutant characters. He's a grumpy gumshoe detective (for those of you who dig the noir) who can't help getting dragged into mysteries involving the whole of the Marvel Universe. He has a very complicated love life. And some of the most argumentative, contrary and downright obnoxious teammates in comics.
Add to this his unique duplicating super power - every dupe having its own distinct personality, many of whom just don't want to go back into Madrox-prime once they finally get out - and you have an endless string of storytelling possibilities. Here's a character who can truly be anything you want him to be... as well as being himself. Go crazy.