You can also find Bison meat, which is also high in protein...and tastes great! Seafood, chicken, and eggs are also the best resources of protein.
I just looked on wikki for you, technically it's dried "Bearded seal game meat", followed by "moose" meat...but you're unlikely to eat those.
Steak is the highest normal meat.
And to add to the current high protein list;
Eggs, peanuts, peanut butter, Nori(dried seaweed), Soya, Quorn, and all meat.
1: Turkey Breast (and Chicken Breast)
2: Fish (Tuna, Salmon, Halibut)
3: Cheese (Low-fat Mozzarella and Cottage Cheese)
4: Pork Loin (Chops)
5: Lean Beef and Veal (Low Fat)
6: Tofu
This is high protein food