I would go with stuff that's hard to buy or expensive in the shops, plus a few staples that you know you'll use regularly. Also think about things that span the seasons as well.
Things like garlic for example can be planted in September, grows over the winter, harvest June/July in time for another short crop like lettuce or radish in the same area. I also have some lettuces and other annual crops planted inbetween things like Sea Kale and asparagus.
For me, I always grow
- parsnips - we eat them by the lorry load and nothing better thna your own parsnips at christmas
- some form of brocolli - PSB, Cavolo nero, cima di rapa
- carrots - but I might stop these as they're always rubbush
- radishes
- a couple of different beans - this year broad beans for early (can also over winter), runner and french
- lettuces
- courgettes
- beetroot
- tomatoes, cucumbers and chillies in my greenhouse (get used in the winter for bonsai protection)
I've also got espaliered apples and pears, autumn fruiting raspberries, gooseberries, and soem new plum and cherry trees. All of these are dotted around the flower beds so not taking up a dedicated space. Only the veg has it's own plot.
What I'm getting at really is think what you like, how much of it you eat and whether your have the right soil (mine's wrong for carrots) and be prepared to experiment.
One last tip - if you grow jerusalem artichokes, put them in containers/ a separate rasied bed, or they will go everywhere - they're a bloody weed

, but very tasty.