Various flowers yes - petunias, snaps, phlox, some mums, some herbs, etc. But it is only an option, not required for anything.

No vegetables that I can think of. At least none of the common ones. Some insist on doing it on tomatoes but it isn't recommended.

You'll find most of the discussions about pinching over on the Annuals and Perennials forums.

Dave

I pinch back pretty much any of my annuals that send up a central stalk. Zinnia, bedding dahlias, pansies, snaps, galardia, petunias, geraniums, verbena, bachelor buttons, pretty much everything but Impatiens, which branch out like crazy without it. I start them early enough that I can pinch them back and they have time to re-grow and be close to bloom when I plant them out.

I confess to being a bit of a pincher too....but probably for bad reasons as often as good ones - all those seeds which I started too early and are getting leggy, those in danger of falling over (staking?tying? I don't think so).....in fact, I am an enthusiastic adherent to the Chelsea Chop, a late May shearing back of numerous plants to keep them sturdy (because I am not staking the bigger ones either). The pinching goes every way - leaders, tips, side shoots (woe betide a wayward tomato or sweet pea side-shoot escaping my eagle eye).

I would say though, it is pretty much horses for courses, entirely optional (I am an inveterate meddler and prodder).