I sometimes do a stir fry with a variety of whatever I have, not just the mange-tout and mini sweetcorn etc. that are often in such recipes. So onion, carrot, celery, peppers, mushrooms, any cabbage, etc., all sliced fairly fine.
Just a little oil then a sauce of 2 tbsps water, 2 of oyster sauce, 1 of soy. I always add garlic, plus ginger and chilli paste too.
Another one I make is a sort of ratatouille - tomatoes, esp. any going a bit soft, onion, garlic, peppers, mushrooms, celery, carrot, courgette when in season. But again, whatever I happen to have that will ‘go’.