Nuts

Shelled nuts are great survival food- particularly if you are on the road because they are so light. The only real problem with them is that they are very fattening and it is tempting to eat them in non emergency situations so none will be available when TSHTF.
One alternative may be fruit and nut chocolate or the famous Kendal mint cake. Mint cake has become a hiking product because it packs so many calories but it may also be found in certain supermarkets.
Boiled sweets can also be a useful but the most important thing of all is water.