In my opinion, Drillbur should be moved in Top A-Rank. Drillbur indeed spins, and becomes a team eater under sand, and unstoppable with a +2. And that's pretty much it.
First, Snover is in every top team except sand. Drillbur will never kill more than one pokemon if Snover is alive. He just comes back after, and blizzard / giga drain, blizzard indeed ohkoes, and giga-drain has got 94% chance to deal 82% of life (18/22). Hippopotas can't come back until he really wants to get take huge damages :
184 SpA Snover Giga Drain vs. 132 HP / 100 SpD Eviolite Hippopotas: 14-20 (56 - 80%) -- guaranteed 2HKO
(14, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 20)
-> Which means 94% to deal 72%
184 SpA Snover Blizzard vs. 132 HP / 100 SpD Eviolite Hippopotas: 24-30 (96 - 120%) -- 68.75% chance to OHKO
(24, 24, 24, 24, 24, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 30)
To make fast, after any kills, snover just comes in and blizzard/giga-drain without the sand team to be able to take his weather back. Well, we all know why is snover S rank.
There's also the problem of priority attacks, which brings a few problems too. Hello, timburr...
It's not about drillbur power in solo, it's about how drillbur fares in a team. He's still very good, but he does not desserve S rank.
Then, I nominate Porygon and Foongus for S-Rank.
They're so incredibly good. First, porygon.
Porygon's stats are 65/60/70/85/75/40. His bulk is impressive, but he also has a very good Satk stat. But the best with him is Trace, and his movepool.
Most of the top-tier pokemons are top-tier because of their ability. Porygon can copy regenerator from foongus, mienfoo, he can copy all the absorbing abilities, which makes him for exemple able of switching into Chinchou, a status problem will be cured by switching into a Staryu, a switch in Murkrow is still the best possibility of using Trace as it allows him to priority thunder wave and recover.
His movepool is still his most incredible part. He accesses to boltbeam, to normal stab/ghost/hp fight, and his stalling part has recover, a move any staller would like to have, and thunder wave who cripple the fighting switches he causes (Not timburr, right) - which is one of the worse things that can happen to our beloved SSS tier, mienfoo. Those are so many pros they clearly outshine his normal type whose (only !) weakness is fight.
Now, foongus. First foongus has spore. Anybody likes to have spore. Especially in LC where the hugest majority of teams are offensive, and haven't any way of countering that (I run insomnia murkrow just for the sake of fucking foongus) Then, he resists fighting type and his defensive stats aren't bad, that makes him a very good pokemon at shuting down set-up fighting pokemon (murkrow is the other best) with his haze ability. He also got a good offensive movepool including grass/poison/hp. Oh, and regenerator, the best ability in the game.
To make it simpler, having a foongus in your team means the ennemy won't even try to set-up as that's completely useless against foongus. I come, i spore/haze, you made me 40% , I made noticeable damages and regained 33% by leaving. Bye.
Finally, I nominate Abra for A-Rank.
Magic guard is so fucking good. I'm especially talking of the sash set here. Abra just comes up and at least kills one pokemon. 105 BS in SAtk, and the glorious 19 speed. His psychic will destroy anybody except bronzor/dark types. It allows him to shut down any set-ups, any sweeper a team is based on (excadrill@sand team, for exemple ?) The few stalls team will also enjoy facing a magic guard user 2shoting anybody better than any wallbreaker ^^
Well, Abra fares well against sweep, against weather, against stall, against normal sweepers, against set-up, against toxic-stallers, against... against anything right ? Desserves A-Rank.