Unripe fruit and vegetables
It turns out I kept picking my cucumbers green. Of course, they were just like the ones in the shops - seedless, pretty bland (although not quite so bland) and 'normal' sized.
I missed one for a few days and picked this giant - about 2' long and 5cm in diameter. Wow. That's what cucumbers used to taste like. And of course do - if they're ripe.
Same with the button squash, I'd been picking fiddly little ones, often a little bitter with a very soft skin that spoils easily. Again I missed one for a few days - and it's a world of difference. If they grow to about 10cm across or more and get the harder outer skin they taste much better (a little sweet) and last much longer (i'm also letting one grow 'all the way' to see how big they get/how it goes - it's about 25cm across after a few weeks).
Green limes - fully ripe limes are light yellow. They taste utterly fantastic and have much more juice too. Although certain varieties, such as the Tahitian Lime can get a funny over-ripe taste, so there is some justification for picking them a bit earlier. But not when they're hard and dark green. But most of the time that's all you can find in the shops (let alone the exorbitant price).
People have been trained to buy this unripe fruit, so nothing else sells. How silly. They must be right down on vitamin C and other nutrients as a result.