@Beartic
Perhaps my usage of Beartic was more specific than I thought it was; I've used it to beat Rain, used it on Rain, checking Fraxure (in rain), countering Meganium (whom I feel is a difficult threat in and of itself, though it is likely purely due to my teams), breaking physically weak thing, etc. etc.... (Also, in my original argument I meant checking Rain teams instead of countering them; I misused the term) But, my points do stand: It IS the only Ice-Type with Swift Swim in PU; it is the only one with priority, and although these are likely smaller niches they are important because it's priority becomes pseudo-STAB under Rain, and it's ability doubles speed under Rain - this, along with it's just-enough (IMO) movepool means it has two useful niches to go on, as well as the fact it isn't dead weight when rain isn't up. Honestly, I would prefer B-Rank, but I would actually be okay with C-Rank.
(btw really the only reason I nominated it was to have it in a rank, really. B-Rank would just be my preference.)
@Throh
I'm not sure if this means anything, but I feel OK with that description.
@Wailord
I too think C-Rank fits Wailord better. While it is a strong attack, it is not ridiculously strong, and Wailord has only got OK defenses, so it can barely take a hit if it doesn't OHKO.
Proedit: I've been testing out a few different 'mons, and I'd like to nominate Staryu for either C-Rank or B-Rank (B-Rank might be a tidbit too high): It's a VERY capable special tank-or-wall(whatever you want to call it...); it's bulk is above average, with 252HP/252SpDef giving it the capability to tank some really good hits;
252SpAtk Cloud Nine Golduck (+SAtk) Hidden Power (Electric) vs 252HP/252SpDef Eviolite Staryu (+SpDef): 35% - 42% (94 - 112 HP). Guaranteed 3HKO.
Recover allows you to come in, Spin, and stall him until he switches. (Or crit, but meh...)
252SpAtk Choice Specs Rotom (+SAtk) Blizzard vs 252HP/252SpDef Eviolite Staryu (+SpDef): 36% - 42% (96 - 113 HP). Guaranteed 3HKO.
Thunderbolt 2HKOs though... Hmm.
I don't really know what other calcs to give you, but it's less bulky on the physical side.
252Atk Machoke (+Atk) DynamicPunch vs 252HP/252Def Eviolite Staryu (+Def): 39% - 46% (103 - 123 HP). Guaranteed 3HKO.
Eviolite Machoke doesn't 2HKO, though, making it a check; on top of that, running something like Psychic typically will...
4SpAtk Staryu (Neutral) Psychic vs 252HP/0SpDef Eviolite Machoke (Neutral): 27% - 32% (100 - 118 HP). Guaranteed 4HKO.
...do OK damage. Okay, okay, bulky Staryu doesn't hit very hard; Offensive starmie doesn't either, though so don't try sweeping with it. BUT, I think it deserves at minimum C-Rank because of it's great utility and above average bulk.
Also, I've been testing out Magnemite (sounds silly, I know) but it is actually capable with Defense EVs. Also, it resists BoltBlizz.
252SpAtk Rotom (+SAtk) Blizzard vs 252HP/0SpDef Eviolite Magnemite (Neutral): 39% - 46% (100 - 118 HP). Guaranteed 3HKO.
This is Modest without SpDef investment. It can Paralyze, hit with neutral STAB, Slow Volt Switch out, or... well, that's it, but it also has other perks: for example, it can use Magic Coat to give the enemy their own hazards, Spores, etc., and it also can pivot from choiced or no-SE-Physical attackers; although it isn't capable of much else. I recommend it goes into D-Rank.
I've been testing out these two for a while, on a number of different teams (I believe 3? 4? I think three.), but I would not turn down contradictory opinions.
Proedit2:
I also plan on looking at Tentacool, although it is already in C-Rank. It's iirc bulkier than Staryu, just with no offensive presence at all and no reliable recovery.