I agree with the beans and Lentils. You can make curries, soups, burgers, nachos with these and add to meals.

Eggs are a great option

You could make soups and stocks from left over chicken bones, old veggies.

Homemade pizza on pitta bread
Meatballs and pasta/vegies
Tuna and rice/pasta
Corn on the cob
roast jacket potatoes with ham, cheese and sour cream