Mind you that I'm only at 21w, so this will probably change...
Most favorite: Feeling LO squirm around in me and watching DH glow as he tells others about our LO
Least favorite: Weight management. I was just barely content with my pre-pregnancy weight, so seeing me getting further away from my target weight bugs me. However, I know this is only temporary and I'll be able to work it off. I have a few friends who are tiny who were telling me about gaining 50+ lbs in their pregnancy (which I can't picture on their bodies), and if they can get back to being their normal size, then I know there's hope for me.