Tuna/mayo with beetroot or sweetcorn or grated carrot and finely chopped red peppers.
Turkey and cranberry
Salami/ham with mashed cheese and avocado
Ham and seed mustard
Hummous and cheese or ham

You can also pre=prepare vegetable sticks like celery and carrot, and keep them in the fridge for the best part of a week. I sometimes freeze individual serves of hummous and take one out at breakfast time, and it's ready to use as a dip for vege sticks by lunch time.

littlelara, the bread does't go stale as long as the bread is superfresh when the sandwiches are frozen, and they are well wrapped without air pockets around them. It's an amazing timesaver.