I'm backing up Delver's argument quoting myself:
Originally Posted by Fat Good Luck! in post 24
Hippo's defense is high enough to resist Drilbur's Earthquake and Scraggy's +1 Drain Punch. It can stall Mienfoo with Slack Off and even suffle the opponent's team with Whirlwind (how does Hippo learn that?). Starting sand is just the icing in the cake for a Pokemon who can support quite few pokemons and teams, from Hyper-Offensive's Drilbur+Sandshrew to Stall abusers like Lileep and Vullaby, even for teams that don't rely on sand, it's a great Physical wall. Hippo is not only the send-in+start-sand&sacrifice Pokemon; it can hold its own with a so-so Attack Stat (unlike Bronzor), solid Physical Bulk and wide support movepool. But, really, if Hippo didn't have Sandstream I would still use it because of its excellent Defensive capabilities, (now you may have guessed I'm a more defensive player)
I agree that Aipom is D, Meowth is mediocre an does Aipom's job better. I have used it with success as a great Flying Gem Acrobatics lead OHKOing non-CS Mienfoo so I can say it's not entirely useless as, say, Pidove.
Having used it more since I agreed with Delver on B rank for Ponyta, I would say I'm tempted to put it in A. But then I recognize one obvious flaw: Fire-typing. Even though Ponyta has the speed to compete with all the top tiers, the prominence of Stealth Rock, Sand and bulky Water-types (Chinchou specifically) makes Ponyta a little less viable than it would. Sure, it is the best answer to all the rising Grass-types, but against Foongus as a regenerator defensive pivot (meaning that it would switch often) or Lileep who has a SE STAB on it Ponyta can't do much.
I'm also agreeing with all of Corkscrew's rankings, adding that Slowpoke's weakness to U-turn, Volt Switch, Murkrows, Misdreavus, Scraggys and its low speed mean that the only common Fighting-type it can wall is Timburr. So~ Slowpoke's utility has dimished in the current meta.
Maybe I'm theorymoning but Skitty is the only pokemon that can paralyze both Sandshrew and Drilbur with Normalize Thunder Wave, a more reliable move than, say Body Slam, Glare or Stun Spore. That being said, it has a very small niche but not worthy enough to be higher than D. I mean, it sure looks cute, and it has the surprise factor, but loosing coverage is a real pain for it in this Meta.
other then that its plagued with horrid defenses which essentially force you into an eviolite (with a max of 15 atk this is a problem cause you dont want, you need, a life orb boost to do any sizable damage) set.
Skitty is not meant to be a bulky attacker so an eviolite is just a waste on it, it's meant to capitalize on Normalized STAB Sucker Punch which would potentially revenge kill Dark and Fighting-types who resists regular Sucker Punch (I'm thinking of Mienfoo, Timburr, Scraggy, Croagunk, Murkrow and others who would easily outspeed and kill it without Sucker Punch; and all of these are relevant threats to the meta). It would be good for a revenge killer once Missy is dead. I'm not saying Skitty is OH SO GOOD but it has a VERY small niche that MAYBE could take it out of E and into D. Anyway, if I DESPERATLEY wanted to paralyze Sand Rushers I would definitely go with Cloud Nine Body Slam Lickitung and wait for the hax to kick in.
Finally, for TR, I think that strategy is meant to be an offensive play as you have a timer on your speed. I can't say I have used it but having played against relatibly good Trick Room Teams (they didn't have Leftovers on Aipom, for example) I can see it's really difficult to pull of and very easy to outstall. Just one taunter (Misdreavus, Vullaby, Cottonee...) means TR is dead. I'm not against it, I'm just saying I'm yet to see a good user of TR. In my opinion, being excellent on Trick Room means D at much. The rest can go play with Sunkern.