It really depends on what you are looking for. I think most folks who have backyard ducks keep wading pools for their flocks.
What do you want from your ducks?
Garden patrol? Looks? Eggs? Meat? All of the above?
I think that you will get a TON of answers as to what ducks are best.
I love my Anconas for foragers, though they have not laid an egg yet. They are pretty, hardy, happy with their pools. I am adding 2 Welsh Harlequin females & a Cayuga female this spring. I want the Cayuga for sheer prettiness, and the WH to lay tons of eggs for my baking.
The Anconas demolished my Japanese Beetles last year without ruining the garden like the chickens, and the pool water was amazing for my garden.
Storey's Guide to Raising Ducks has a very informative section on many of the backyard breeds - common & uncommon - that you may find helpful.