Chicken though it's a closs toss up with beef. My meal plan (trainer made it) calls for 8-10 oz of leanish meats for lunch and dinner (along with a crap ton of veggies). I normally have chicken for lunch (stir fry) and do either steaks or turkey for dinner. We do throw in some pork loin every once in a while and I do occasionally add a crumbled piece of bacon to my daily eggs in the morning.
I still love beef the most of all though chicken as grown on me. I can't stand the taste of fish except if it's breaded and deep fried so I don't tend to get much of that anymore. I do take those yummy fish oil pills daily... learned the hard way to go for the coated versions!