There are so many choices! It really depends on so many things. Greenwings and Scarlets are some of the most beautiful and flashy. It's hard to compete with those amazing red feathers. Blue & Golds and Military macaws are other common species. All of these macaws are pretty big and their beaks can be very imposing. Make sure you're comfortable with a bird that size on a one-on-one basis.
We have a Red-front macaw which is less common. They're also much smaller than the ones mentioned above. Just like Willist is sure his Greenwing is the best; I'm absolutely positive that my RFM is lightyears better.
It really depends on what you want. Do you want a cuddler? Flyer? Talker? Is size a concern?
The only direct experience I have with macaws is with our red-front and our friend's blue-throat. I'm very happy to give you more information on those. Both are smaller, but not mini-macaws. Let me know if you're interested.