Well, my standards for snacking are yours: carrots, celery, broccoli, and cauliflower. I love cauliflower. And cucumber, cucumber is brilliant. I always have salad on hand, and I really like the broccoli slaw they sell. Made from the broccoli stems (which are edible if you do them at home and taste really good when peeled and chopped and steamed) - I use it to make a bagged salad more interesting on those days I am not interested in chopping.
Jicama! Round, nobby, funny looking - not huge flavor but nice and fresh and crunchy, with an engaging bit of sweetness. And really lovely with Tajin seasoning: http://www.tajin.com/en-us/tajin
I picked up some fresh cut jicama with tajin seasoning for a snack on a recent trip and fell in love with the combination.