I'm rating this loosely, but I base it on my neighborhood & dog park:
1) Labs
2) Poodles/mixes
3) Pitties/mixes
4) Golden Retrievers
5) Yorkies
6) Mini Schnauzers
7) Australian Shepherds
8) Boxers
9) Chihuahuas
10) GSD's
I just looked it up, and these are actually the top 10 most registered breeds in my area (of course... doesn't include the mixes):
1) Labrador Retriever
2) Yorkshire Terrier
3) German Shepherd Dog
4) Dachshund
5) Golden Retriever
6) Chihuahua
7) Miniature Schnauzer
8) Poodle
9) Shih Tzu
10) Tie: Boston Terrier, Pug