I have been testing soylent for the last 3 weeks to replace 1000 calories a day (approx. 1/2 of my caloric intake) mainly for eating healthier foods and I am testing it to see if I can add it into hunting/camping diet. It gives all the nutrients that you need for a whole day (on a 2000 calorie level) and could theoretically replace all of my food. I always seem to be drawn to tasty, fatty and generally unhealthy foods. It tastes very mildly sweet and has a light vanilla flavor. I haven't tried adding flavors to it yet as I like the taste on its own. You can look at it at soylent.me
If you like peanut butter, PB2 is a pretty good powder that adds flavors to things or in place of peanut butter (if you hydrate it) without the weight and fat. I eat it with pilot bread, which you may have a hard time finding outside of Alaska and Washington State.