Herding: I feel that ACD's are a very drivey breed & completely dedicated to their job. Border Collies have the eye and have great drive as well, but as a breed, I have met many more ACD's that will herd anything all day long and are very versatile with what they can work. I actually cannot think of one ACD that I know that doesn't exhibit strong herding behaviors on most moving objects. Of course, I l o v e Border Collies, and watching them work is incredible - but for intense herding drive, I would definitely pick ACD's.
Sledding: Sibes are extremely prey-driven and an amazing sledding breed, for sure. But there are lots of mixed breeds (Alaskan Huskies) that are so nicely bred by experienced mushers.
Patrol: I think all of the Belgians are way under-rated. GSD's are awesome dogs, when well bred. But, I have seen working Belgians that a GSD could not touch.
Sporting/Hunting: Definitely field-bred Labs, they live for it, and are so versatile. I have also seen some amazing GSP's work.
Terriers: A well-bred JRT has crazy drive! They will follow a rodent, or a lure, anywhere!
Sighthounds: Greyhounds, for sure! It is amazing to watch them run, and I don't know of any Greys that can be trusted off-leash... if something catches their eye, they're gone.