Favorite wood? Hard to answer with just one. I like a lot of them for different reasons. The most important thing is to match the proper design to the species of wood. With that aside, some woods that I like:
Osage: high compression and tension strength. VERY durable. Resistant to rot. Beautiful.
Red Mulberry: Osage's cousin. Same benefits, but to a lesser degree. While not as springy or as dense as Osage, it seems to grow straighter and have thicker rings. My workhorse bow is a red mulberry bow.
Pacific Yew: light as a feather, resistant to rot, makes a great bow. Easy to work. Beautiful. Very hard to afford/find quality staves (I have my stash, though). Easily dented, and little sensitive to cold weather.
White Oak: strong in tension. Easy to work. Grows straight. Plentiful. Dense. I see it as hickory without the moisture retention problem. It's becoming my favorite whitewood.