i think sableye and mandibuzz are both viable lol. Mandibuzz has Whirlwind, Knock Off, immune to Psytrike or Psycho Boost, it beats Deoxys-A lol, obviously not those with Life Orb Thunder but i can survive one.
We shouldn't forget Lapras, Lanturn, urgh Frillish. Poliwrath sucks.
i think sableye is the best on that list lol. pineco is outclassed by forretress, tangrowth has no special bulk, mandibuzz is ok it can check ghost arceus and taunt base 90s. walrein is only good in hail lol.
lol the point is that gyarados is neither relevant enough to ubers, nor possessive of unique attributes to be mentioned speccifically as 1 of the 2 lugia checks which can take ice beam and taunt it........