I think it really depends on everyone's individual definition of "Jack of all trades", and to what extent each "trade" is used, needed, etc.
For me, the Doberman Pinscher is my ideal Jack Of All Trades - but their trades range in importance, although the breed is known for doing almost everything... it's just that they do things more readily and better than others.
Herding - yes, there are dobes that herd...
Retrieving - some dobes are retrieving fools - Ilsa is one of them.
Hunt - there are hunting dobes, from what I've seen they're mostly in Europe
Tracking - one of the Dobe's stronger "trades"
SAR - another strong point for dobes
Watch/Guard - the Dobe excels at these!
Pull a sled - I've seen it done, and done reasonably well!
Guard against predators - again, a Doberman strong point. A good dobe is fearless, and will happily take on a beast twice or thrice their size in defense of their master.
Therapy dog - Yet another venue a dobe excels at.
Companion - IMO, the best dog for the job!
Dobes are my Jack of All Trades - but then again, if I was a rancher, or a person who lived in the Far North, or someone who couldn't control anything more than 50lbs (or have the ability to deal with a strong-willed dog)... the Doberman would NOT by my Jack Of All Trades!
A good GSD though... now that could be interesting! I could see a good GSD pulling a close 2nd...