Fish, especially well sourced fish is the consensus choice / best protein you can eat. 

Fish from clean waters, wild caught / never farm raised and high in Omega 3s - that's the good stuff. Here's where I currently buy my fish...

#1 Wild caught salmon from Alaska. Tony and his crew do it right; fish for 4-6 hrs, fillet, vacuum seal and flash freeze. They ship anywhere, your foam cooler full of salmon fillets on dry ice is shipped two day air and arrives hard as a rock.  Makes sense to order a lot so that the shipping cost is spread over more pounds of fish. Call a few friends, do a group order - they'll thank you when they see and taste this crimson red buttery salmon.

#2 Lake Trout from Canada. Light flaky tender lake trout, relatively high in omega 3s. My source also sells walleye which is the best I have ever had. Same shipping and economies of scale apply here.

#3 Another great source is a family run fishing coop out of Golds Beach Oregon, Fisherman Direct. They catch and stock a big variety - tuna, halibut, flounder, shrimp, scallops etc. All sourced from clean waters and shipped frozen. Great way to get a big variety in one shipment.

Lastly, if buying clean protein like fish in bulk makes sense then having a chest freezer in the basement does too. Especially when you can get a nice 7 cubic ft unit delivered to your door for about $250 via Amazon. It only costs $35 per year to run and provides you the convenience of always having clean protein ready to rock any time of year regardless of the season.