When I was a kid - if used to be Frosted Flakes, (cuz of all the sugar.)
Now as an adult, Its Honey Bunches of Oats (if I can afford it), Sunshine Snacks' CornFlakes (no sugar or anything - just plain flakes), Post's Shredded Wheat (if I can afford it), or Universal's Brand Flakes. Every once in a while if I feel snackish for something chocolate and can afford it, I'll try to get a box of Post's Cocoa Pebbles to consume as is, with no milk etc.