Old pizza is a staple here, same with leftover chinese food my friends bring back when they go out to eat (while I pay off loans lol). Can't forget the ramen pb&j (use 2 ramens and put pb&j on it), it comes out cheaper than bread if you buy in bulk and there are always people with free pb&j they aren't using (just watch your sodium count)
. The best thing is it never tastes that bad because you always feel adventurous doing it (and it's cheap... that always makes things taste better).