I haven't seen anyone list sour cherries, but when we lived in zone 3 in the prairies, ours were reliable producers and my favourite summer fruit. We had the old tree type - probably Montmorency, or perhaps Evans.
My saskatoons were wild, and I picked buckets and buckets of them, and we had a large patch of red raspberries, plus Red Lake currants and of course, plenty of rhubarb. We had crab apples, and two eating apples - one very green and tart, and one delicious one i suspect was Goodland, but on a standard rootstock and in shade so it produced very few apples, and i only got the (treasured!) windfall, a few apples per year. And crabs, of course. And strawberries were reliable, and delicious too.
My dad is still in zone 3, but Ontario - he hasnt had any success at all with the modern U Sask sweet sour cherry bushes or, sadly, saskatoons, which i planted 2-3 times before giving up. He has managed to grow grapes - i think i planted Valiant, and he gets an occasional large bumper harvest from them. I suspect if he pruned them, more would ripen! Balsor's hardy blackberry died (possibly due to where he planted it!). Haskaps have grown well for me in Zone 4 Ontario, and i suspect would also do well in Zone 3. Things tend to die as much from baking in drought and shallow soil over bedrock, as winter kill, though.
I think living in Zone 3 really teaches you to treasure fruit, even tart fruit. I still enjoy chewing raw rhubarb, currants straight from the bush, and prefer sour cherries to sweet cherries.
Still, i am enjoying my move to zone 6!
Edit : oh! And i really enjoyed our wild Canada plum on good years. Some years the fruit was really tart and dry, but on good years, it was fantastic and a punch of flavour.