Beetroot- and radish tops are fine for salads (as are young dandelion leaves, though you probably don't cultivate them)

Nasturtium leaves as salad are not much to my taste but may be to yours. You can pickle nasturtium seeds as a substitute for capers, I've had those (fair to poor) but am not fond of capers anyway so my opinion is probably best ignored, I don't have a recipe.

Peapods are a decent vegetable steamed or sauteed in a little butter, but they need to be well picked over, and not too mature.

Courgette flowers can be battered or stuffed, the Italians seem fond of them.

Careful does it with the bean family, some are only safe if well cooked.

Apple pips are ambrosia to some, but contain a cyanide precursor which means your body will make a little cyanide when digesting them. Consumed in moderation the body will deal with this small quantity without noticeable effects.