I like that he's a goofy idiot who is close to becoming the World's Strongest Swordsmen by holding a sword in his teeth.
I also like how Zoro treats younger people, his interactions with Chopper where he acts like an older brother are really fun and nice.
Most macho characters are kind of... empty of emotion, like Mihawk, and I like how Zoro is full of emotion and passion, but tries to control those feelings to strengthen himself.
At the end of the day, I'd just like to live around someone like Zoro. When Oda said he would be a police officer in real life, I think Oda meant that Zoro wants to protect people and keep the peace, but he does it in his own style.
Also, really respectful to women and children.
Zoro is the kind of person who would never make the sacrifices the Marines make, and be willing to murder innocent civilians just to destroy his target. He faces all of his fights head on, without trying to use other people as shields. That's why Marines like Tashigi and Smoker can't help but admire Zoro, despite him being a Pirate; becuase they serve a force that openly uses its power to destroy weaker people, when so called "Evil Pirates" like Luffy and Zoro never try to destroy weak people, and instead help them. Alabasta is one of my favorite arcs because of how it showed Smoker and Tashigi realizing that Luffy, Zoro, and the Straw Hats really WERE good people. They said they would hunt them, but, Tashigi let them go when she had the chance to arrest them.
In terms of true justice, I think Zoro is one of the most moral characters in the series. Always helping people while bitching about it.