The Houston Press put together a slideshow of twenty foods from TV, movies, and literature that they wish really existed. Entries include Romulan Ale from Star Trek, Harry Potter's Butterbeer, and the "tomacco" plant from The Simpsons (an addictive hybrid of tomato and tobacco).
I'd add in the fizzy drink Frobscottle, from Roald Dahl's book The BFG—tasting "of vanilla and cream, with just the faintest trace of raspberries on the edge of the flavour." And coolest of all, the bubbles go downwards. What fictional foods would you like to eat?