Hayate no Gotoku!

Also known as:  Hayate the Combat Butler

Hayate is a super-unlucky 16 year-old-boy who ends up shouldering his parents' financial havoc. By chance, he rescues Nagi, the well-dressed little heiress to a mega-rich family from hoodlums, then he gets hired as a live-in butler that guards her from all sorts of troubles. His career, however, requires more than just mental and physical strength: he needs to be entertaining too!

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Producers, official website and other details: AniDB, ANN, Wiki