Best and lightest is the 1 or 2 serving size of Mountain House freeze dried food. It will keep for years and years.
The only disadvantage is you have to add water to it. Heated water if possible.
Buy it here:
http://astore.amazon.com/thebugoutguy-20/detail/B0002YRNJK
If you want something ready to eat that might be cheaper(but heavier) then I would recommend chef boyardee spagetti with meatballs which doesn't taste half bad cold.
Maybe smoked oysters, beef jerky or small cans of tuna or chicken. Peanuts are good too.
Don't forget the can opener or the swiss army knife to open cans though.
http://astore.amazon.com/thebugoutguy-20/detail/B0009KF4GG
