I agree with fresh herbs, they don't take up much room and you typically don't need much and they can be super expensive in the supermarket. Basil hates even cool weather, anything under 55 and it's not happy, but rosemary parsley cilantro chives thyme sage and oregano will tolerate cool temps and even light frost.
Given your location, you can also rotate.. kale and lettuces (arugula is my favorite) and sugar snap peas are delicious, easy to grow from seed, mature quick and like cool temps So you'll get a jump on the season. They quickly go to seed or die back once it gets hot, so you switch.. if you have a fence (or trellis) cucumber can be prolific in the summer and can be trained up. Eggplant and peppers also give you good bang for the buck, in terms of space and time.
If you have the space and are willing to do something to keep the birds out raspberries are always delicious and can be really expensive in the stores, but you only get one harvest a year, and you only need a small group of birds to wreck all that work in an hour. One morning you have nice pink berries almost ready and by lunch they're all gone. I've never had luck with strawberries. They're easy to grow, but the fruit is always small and really seedy, and you get like 3 a day all summer long, never enough at a time to do anything but pop 'em in your mouth while you water or weed so I don't bother.
Tomatoes will work in the summer, they are sooooo good off the plant. I only eat tomatoes from a garden, and then I can live off them, but you're growing season is short, tomatoes need hot. I advise you to search for a determinate species that ripens early, usually cherry and grape mature faster than a beefsteak.
Zucchini are easy, prolific but they're BIG, the plants can take up a Lot of space. And they are cheap in the supermarket. The benefit of growing your own is 1. The plant is actually ver pretty, and 2. You can harvest and eat the flowers.. put a scoop of goat cheese inside, dip in flour and flash fry... yummy.
Speaking of eating flowers, Nasturtium are great because they're pretty, easy, and the flowers are edible.. we eat with our eyes, throw a couple nasturtium on your salad and you really want to eat it! They're sharp and peppery, so you wouldn't eat a bowl of them, but they add a nice zing to a lot of dishes.