If someone tells you that your favorite pokemon has no possible viability competitively, you shouldn't just accept it. The fallacy police can swoop in and tell you it's fallacious for reason of bandwagon or authority appeal fallacies if they speak softly and carry a big smogon copy paste, but you should just be ready to stick to your guns if you love the pokemon enough anyways.
Anywho.
Walrein.
You could try physical, it's got the bulk and sort of has the stabs. Invest in HP and split between Atk and Def; probably impish or adamant. Give it curse, to boost its attack and defense - if you take that route you could make it Brave, and run it on trick room team. The defense investment and curse will work nice to cover its rock and fighting weaknesses. With curse boosted stats, it can make very nice use of Aqua Tail (tutor in ORAS, not sure what your situation is, battle spot singles I hear?) and Ice Fang. Backing that up with possibly Crunch, Iron Tail, or Earthquake, and you could make a run of it. Have it hold leftovers for a longer life possibly, or a life orb for extra punch.
If you want to keep it special, make it modest or quiet to play the most on its higher sp atk since it has no special boosting moves. Obviously, HP and Sp Atk EV's. Also obviously you'll want Ice Beam, Surf OR scald, but not both. Signal Beam is a wild card coverage move, and Icy Wind can slow opponents you can't KO down for teammates. Check its hidden power type- it it has synergy with its other attack types, use hidden power on it. If you run all attacks on it, you could give it a vest, and make it exceptionally bulky. If you don't, and have the fourth move slot, give it rest - and have it hold that Chesto Berry.
Don't let someone tell you there's only one way to play the game, or that things you like can't be used though mate. C'mon. I'll post this again.