I know I'm repeating myself here but I think this deserves special recommendation.
Mahou Sensei Negima x100000000000000000000000000
Incredible, incredible series. Godly. My second fave actually.
First 15 chapters are bad. No doubt about it. But around chapter 16 it starts picking up giving a glimpse of its true potential. Then it gets a bit fuzzy again around chapter 25. However when the Kyoto arc comes around like chapter 40ish, it detonates, I repeat, DETONATES in quality to the point where your mind is crushed into a bunch of mushy goo. Now it's one of the best shonen around on par with HunterxHunter and One Piece.
Story: Incredible. The arcs can get pretty complex yet Akamatsu never loses track of any of his story points and goes out of his way to draw simple diagrams to explain to the reader what's going on. The plot twists are so good just thinking about the complexity of an arc fills me with pleasure. Seriously, the school festival arc was filled with time travel headaches yet Akamatsu flawlessly tied everything together into a tapestry of awesome.
Story-telling style: Akamatsu has a pretty happy-go-lucky style that plays around a lot with tropes. it's pretty fun, refreshing and gives you confidence that this author knows his shit.
Comedy: Hillllllllllllllllllllllllaaaaaaaaaarrrrioooouuus. Like I said, Akamatsu plays around with tropes a lot. It's a prevalent part of his story-telling style. S obviously he knows what hits the funny bone:P
Characterisation: Godly. Nothing else to it. I can never decide who's characterization I like more, Akamatsu's or Oda's. Akamatsu flawlessly balances a 30+ main cast complete with oodles of side and minor characters!!! And it is possible that it'll grow to 40+!!! (Depoending if there's an arc after the current or not) Basically Akamatsu had a 2 page a class register and has almost completely given each and every member of that register equal development and spotlight. Especially awesome characters are Jack Rakan (man among men!), Evangeline Anathasia Katherine (Kitty) McDowell (Eva-sama <3<3<3), Nodoka Miyazaki (I love her so much), Negi Springfield (extremely unique shonen protagonist), Chisame Hagesawa (the only one who tries to keep a grip on reality), Ayase Yue, Sakurazaki Setsuna, Kagurazaka Asuna…oh fuck it, they are all awesome.
Art: It's background porn. No other way to describe it. Incredibly beautiful and detailed. Great creative designs. Perspectives are sometimes a bit funky at rare occassions but every great artist has his flubs here and there.
Fighting: Great fights with plenty of strategy and action with a visual display that's extremely impressive.
Power Display: When a top class warrior is taken out by a far, far weaker character in an awesome fight and it doesn't screw with the power level, you know the author is doing something really right.
Weaknesses: Ecchi. Quite a bit of it. But hey, NOTHING can be perfect. It's like a toll to compensate for the sheer awesomeness of this series. It's Karma.
Final remarks: If you love shonen and haven't read this series, you are missing out on a lot!!! A must read!!!