I like the idea of freezing the sandwiches!
Back to the subject...
Peanut butter and jelly, of course.
But how about peanut butter and honey...Peanut butter with sliced apples or bananas..or peanut butter and bacon?
Speaking of bacon, how about bacon and cheese...or cheese with fruit? I don't know if you could carry grapes, but you could certainly slip an apple or pear into your bag.
You can buy individual serving size cans of tuna, chicken or ham with easy open tab tops. Pick up some little plastic packages of condiments from the deli, and put bread or crackers in a ziplock. Voila...lunch.
Vegies like broccoli, cauliflower, carrots, snow peas, sweet pepper strips, celery, etc, hold up very well, and you can bag up what you like. Sprinkle with lemon juice and salt and buy one (or two) of those individual serving size cups of salad dressing from the deli for a dip...just in case you want something healthy to go with your sammy.