Well, oh GreatSage, he did say:
Gyarados will Dragon Dance while you are Taunted, to the point where Waterfall can OHKO.
Now on a typical Bulky Gyara VS typical Gastrodon that requires the dragon to DD 3 times for a guaranteed KO. Now what on Earth would force Gastrodon to stay in and Counter while Gyara DD's 3 times? Well, I can only think of one thing and that's a trapping move. Hence the Mean Look comparison.
No problem about the Fake Out confusion either. Sure woulda been cool if it did activate on a switch! Would be a way to counter that damn irritating monkey.
And as for the original thread question, I'm gonna say Empoleon. I thought the weakness to two of the most common moves on the game would screw him over, but whilst using him, it seems he can switch into damn near any move on the game, take minimal damage and dish out powerful Water/Ice/Grass moves from 111 SPA. Plus some great support moves and an ever-useful ability and I have a new favourite. ^_^