It's very difficult to categorize Hayate no Gotoku in a specific genre. On the surface it is most obviously a comedy, but of what type? Situational? Slap-stick? Dramatic? Parody? Hayate no Gotoku is in fact all of these, as author Kenjiro Hata seems to be ill content with sticking to a single source of comedy. The first chapter alone contains: the titular Hayate riding head first into a subway entrance, fighting off Yakuza, referencing biblical stories, referencing Gundam, and a cameo of Santa. All wrapped up in the 'poetic' first chapter title: "Santa's Red is a Blood Colored Hell," and we have a good point of reference to determine the tone of this manga.
Yet perhaps I'm being unfair. Hayate no Gotoku is a very effective comedy, but it is more than that. In it's parody of action anime, we see well drawn fight scenes, both filled with drama and dripping with irony, both mocking and reveling in the straight faced cliche. Hayate has its dramatic moments as well, and while Hayate may laugh it off when questioned by other characters, the reader feels more than a little sad for Hayate, who's been sold to the Yakuza by his own parents. The plot (if it could be called that) also revolves around elements of romance and harem, as Hayate somehow manages to earn the attention of every cute girl within a 100km radius. Kenjiro Hata pushes the action, and the drama, and the romance as far as it can go... before a side character drops a deadpan snark, or Hayate says something tactless yet again, and brings the whole thing crashing back down to its roots: a parody that fools the reader into thinking it's taking itself seriously, before yelling "gotcha!" and pulling the rug out from under everybody's feet, including its own.
Kenjio Hata creates a world in which the utterly impossible can happen, yet at the same time each and every character is very real. Beyond his comedic genius, perhaps one of the best indications of Hata's writing prowess is his ability to juggle so many characters (the cast of Hayate no Gotoku is huge, easily topping 25+ main characters by the time the manga is in full swing) yet giving each one a distinct look, set of mannerisms, and a 3D character. It's no wonder that many a shipping war has been waged over which of the 20+ lovely ladies Hayate will inevitably woo. Each girl gets to share in the spot light, and if they do happen to be gone for more than ten or so chapters, don't be surprised when the show up again, angry and demanding they get more panel time. This leads the the most dynamic of Hata's genius: his treatment of the fourth wall. Does Hata break the fourth wall? Perhaps he doesn't go that far, but he does bend it, crack it, warp it, twist it, sit on top of it, dig under it and paint thing hot pink. It really is a dynamic and wonderful form of comedy that needs to be experienced first hand to appreciate.
The art in Hayate no Gotoku varies, though most of the time it is a touch on the simple side. Characters are drawn simply, with standard anime overreactions as the situation calls for. Yet this does not stop Hata from cranking out a beautiful spread every now and again, whether it is of a night time city illuminated by its lights, viewed from the balcony of a clock tower, or a simple hug of two old friends reuniting. Hata has no shortage of talent, but he knows when to apply it, and when to keep things underplayed. This is not Berserk: not every panel needs to be lovingly rendered in order to convey every subtle detail of the world. Perhaps a good way to sum up Hayate's art would be: it works for what it needs to do.
I can honestly say that I don't think there is another manga out there that is anything like Hayate. Comedy manga tends to stick to one or two types of comedy, and roll with them. Hayate seems to try to blend everything it can, and somehow still have a concrete world and overarching story. It is a special manga that can some how manage to make me laugh out loud every week, much to my roommate's annoyance. It's an endearing manga that makes one care about the characters and the world, and enjoy both its comedic and dramatic moments. Anybody who is a fan of laughing (and really who isn't?) should check this manga out. It is a bright star among the genre of comedy that somehow manages to transcend its genre, yet still excel at it.