I saw a thread you posted some time ago about Gyrados and Gengar.
You made a good point about Gengar's typing based on Gen I game mechanics (Note: there is a glitch in Gen I where Lick wasn't very effective vs. Psychic types) and that made sense, but I think its typing is good and a senseable Poison type, as it is a haunted gas cloud (somebody mentioned this in the thread). Given game mechanics as it is, changing him to just ghost would greatly weaken him. Also, what is a better visage of death than a sentient poison gas cloud?
As for Gyrados, there's some speculation about a switch around of its sprite. Consider Dragonite as the last form of is chain, then compair Dragonaire to Gyrados and Magikarp to Dragonite. Gyrados/Dragonair share the similar body type/coloring, as do Magikarp/Dragonite. Dragonite's Antenne look almost identical to Magikarp's Whiskers, but upside down. As for Magikarp's "origin" story, it's based on an old Japanese legend of an ugly fish that wanted to be a dragon, so it JUMPED OVER A MOUNTAIN and *POW* Dragon. Now this explains his typing as Water/Flying, and what may have supposed to been his wings renforce it (And it looks like a Dragon "should" look like, thus completeing the story). The only "lose end" this sprite switching leaves is how can Dragonite (Gyrados Sprite) fly without wings? But if it were a dragon, nobody would really care, because Dragons are magical.
Also, anybody who thinks Pikachu can reliably kill Gyrados is dopey. Pikachu may be faster, but Gyrados' Sp. Def is twice Pikachu's Sp. Attack. This may be negated by Pikachu's Light Ball, but all that set up does is kill one very specific Pokemon sometimes (Remember, Gyrados can equip Assault Vest and Berries that reduce damage, or have a focus sash), and if Gyrados wins, Pikachu dies. Really, the electric weakness is probably the only thing keeping him IN OU, rather than under the BAN HAMMER, as with all super strong Pokemon that have a 4x weakness.