What I love about One Piece:
1. The Story. It's brilliantly contrived and tight-woven, yet open enough to allow for doujinshi like crazy. There's a huge world and the story is happening in a small part of it. It's up to the reader to imagine the rest.
2. Luffy. The man is a combat genius. And yet, he's an idiot. I mean, All Son Goku knew how to do was train until his muscles exploded and then keep flinging himself at the enemy. Luffy uses strategy. He actually creates techniques that aren't based purely on training for 100,000 hours. He takes full advantage of his rubber body.
3. Robin. Tragic past, tragic heroine. Robin is the star of One Piece, right on equal level with Luffy. She's brilliant, tortured, unique, and mysterious. It makes for a perfect character for the story to center around.
4. Recurring characters. Who would've guessed about Garp? Or Shanks? Or anyone else, for that matter? Almost every character that hasn't been killed has come back.
5. Deaths in One Piece are only if necessary, they're not forced. I mean, look at Shaman King. Why did Lilirara have to die? Why did that bear have to die? What purpose does it serve to have a whole bunch of people die? Yes, people die, but in One Piece, it's only those that need to die, like Shura, or Spandam (Here's hoping).
6. The Grand Line concept. Opposing magnetic fields. Weather phenomenon based on currents going under two mountains that creates dead air. Knock-up Stream. Oda has explained most of it, and it's very logical.
7 The flashbacks. More than anything, they show that powerful people have always existed. Norland, Calgara, hell, even Belle-Mere was no joke.
8. Pirates. Enough said.
