Grass-fed beef is nature's health food. Its expensive, but probably by far the best meat for the majority of your meals. Bison is also a great option.
In general, as far as land animals go, go with either wild/grass-fed or very lean cuts/meats.
With fish, generally smaller is better. Larger fish tend to have large mercury levels. Always get wild fish if possible, you dont get the contaminants and you still get the great profile that you lack when you buy many farm-raised fish. Alaskan Salmon is great.