One of my all time favorites is simply buttered toast. It's better if the toast is a multigrain bread like Dave's Killer Bread. Another great alternative is cream cheese on toast. Drink some black coffee with this, and it's better than many things that take much longer to prepare.
A peanut butter and jam sandwich is easy and tasty also as long as the components are of good quality, i.e. actual jam or fruit preserves, NOT jelly. Neither Smuckers nor Welches can be the brand since they are both totally mediocre at best.
I'm not sure these count since they take a bit of time to prepare, but I also really like sautéed asparagus, sautéed mushrooms, and onions either sautéed or raw (although onions upset my stomach by themselves; they're like eating peppers by themselves in that they just sit there and burn).
What quick and easy, low ingredient foods are your favorites?