Orange blossom water would make a magical addition to your store cupboard.
Barberries, or zereshk, are tiny dried red fruit with a tremendously sharp flavour. They come from Iran, where they're used to add freshness to rice and chicken dishes.
Marinating chicken in miso adds lots of character to the meat with little work.
Dried porcini add a substantial, deep flavour to otherwise more neutral vegetables. I use them in risottos, mashed roots and winter soups.
The addition of vinaigrette to freshly roasted vegetables gives them a freshness and juiciness they don't normally have; the acidity brings out new shades of flavour, too.
My secret with kale is to add lots of sweet or sharp flavours to offset some of that grassy intensity.
Chinese sausage, which is widely available from Asian grocers and online, is sweet, rich, and enticingly smoky. I add it to steamed rice with strips of omelette and a few baby veg stir-fried with soy.
Pomegranate molasses is ubiquitous in Arabic cooking: it's sweet, sour and adds depth.
Good-quality nuts, toasted in a little butter and salt, make a magical addition to many salads.