The ultimate sandwhich filler, dip or nacho topping is Gucamole. Its so easy to make and is delicious. You should make your Guacamole by hand rather than using a food processor as doing it by hand gives it the right texture needed.
If you have a shared lunch at work bring a bowl of Guacamole with some crackers and a few vegies such as carrots and celery.
For A Great Guacamole Recipie see http://www.marthastewart.com/page.jhtml?type=content&id=recipe1380.