The Mayans were wrong about the end of the world and the rapture did not happen, but that does not mean we are out of the woods yet. There are many ever-present threats still looming and a doomsday event could be nearer than we realize. Provided you are thoroughly stocked up on weaponry and survival tools, one question remains...what are you going to eat?
MREs have been relied upon for years as a means to conveniently carry around a self-preparing meal. They are, of course, property of the military so you are going to have to hope that during an apocalyptic event the military will share. They have been generous with their MREs in the past during events such as hurricanes and such, but the military might be too busy to dish out food when the world is ending, so counting on them as your sole food source is not advisable.
Unfortunately the nature of foods with long term potential means you are not going to have access to fresh fruits and vegetables, so you are going to have to rely heavily on items laden with preservatives. If you plan to be in it for the long haul, your food will have to make that same commitment. This may not be the healthiest for you, but no one promised the end of the world would exclude places like Panera Bread and Smoothie King for healthy options.
In line with preservatives and fruit-like taste, however, is Jello. With both a hot and cold water method, you have two ways to make it depending on the water you have at hand. That said, you're going to need water, but hopefully that was already something you thought of and put pretty high on your list.
Then there are Twinkies. Granted, they disappeared from the market, but they are back and hopefully better than ever. Twinkies have a reputation of being long-lasting, but Hostess has stated in the past that the lifespan of Twinkies is truly about a month. That is probably an 'ideal' eat-by date (have you ever seen moldy Twinkies?), but to be on the safe side, eat your Twinkies first.
Another option is processed cheese. Make sure you are buying actual processed cheese as opposed to that pesky 'real' cheese that pops up from time to time. Those individually wrapped cheese slices in the grocery store only have to legally contain 51% cheese and once that has been achieved, all bets are off. This means chemicals and preservatives, which in the case of an apocalypse is a big, fat yay!
We can't forget about Spam! Sure, canned goods as a whole, be the cans of meat or otherwise, are an excellent idea, but Spam in particular is beneficial because it is salty. One serving of Spam contains 33% of your daily salt allowance. Bonus if you eat your Spam while wearing one of those cool Spam t-shirts that were so popular in the 90's. Double bonus in that you may be too salty for the zombies to eat you first since those around you may be more appetizing to the zombie palate.
Also on the apoca-list is nondairy creamer. Sure it seems useless without coffee, but did you know it is flammable? It will literally explode upon contact with a spark, so don't store it near the matches unless fire is your goal.
In truth, there are many excellent selections for a long-term food stash, and some of what is mentioned here will kill you faster than an actual apocalypse. Canned goods, rice, honey, and hard candy are a great start, but beggars can't always be choosers and sometimes choosers have to suck it up and pass the Spam.