Easiest of all (though only sub-tropical) are kiwi fruit. I've had them
germinate after winter in the compost heap. One of them having survived
several winters with no protection, is currently making a robust
territorial bid on our somewhat crowded front fence.

The very hairy red stems and big leaves lend a jungly exotic look though
its unlikely ever to bear edible fruit here in Scotland.

I've found lychees easy to germinate but didn't make a plant
interesting enough to bother keeping.

Janet.