Pekins- My pekin are really good layers, I get an egg a day most days. They are molting right now and aren't laying yet though.
Cayuga- I only have one female layer, she is a really good layer. She also lays black eggs. I know, sounds weird, but they look really cool. Although, not all cayugas lay black/gray eggs, most lay white.
Khaki Campbells- I have only had one, make it to adulthood. Although, it was winter so she never did lay any eggs. They are supposed to be really good layers. She was really sweet yet really shy.
If you want a pretty bird, I've always thought that rouens were pretty. They look just like mallards, but they are heavier so they can not fly. I have not had one yet, but plan to get one this year.
I would advise not to get mallards and/or muscovy unless you are willing to keep their wings clipped. I tend to avoid any flying ducks, but you may think differently.
You can avoid ducks being aggressive if you handle them enough. I got my first male as an adult 'cause the feed store didn't sell boys, only girls. Anyway, the male was really aggressive at first, but after being handled just about every day, he grew out of it. I've had three other males since then, and none have turned out that way.