Yeah Im not nominating any of these just yet, but I think they should have discussion:
Imposter: I don't think this is that great, infact for some actually good pokemon, its a detriment.
Moody: As I discussed earlier on this very page, moody is banned, it should get its own tier.
Flower Gift: Since we are not including the effect in doubles... this should be F tier.
Analytic: Currently nothing good gets low speed and high special attack with this ability, but if something did, I could easily see how this ability could be put to full use.
Shed Skin: Sure its luck based, but the ability to passively heal from status is pretty great, in some situations its better than natural cure
Infiltrator: Again I could see quite a few offensive pokemon loving this ability to slice through screens.
Inner Focus and Steadfast: Immunity to / speed boost after a flinch ain't that great.
Pressure: I think that this has more use there we are giving it credit for, Kyurem this gen and Zapdos last gen are able to use PP stall sets thanks to this.
Iron Fist: Pokemon with punches love this
Pickpocket: Seems rather situtional or gimicky to be used, a few customized sets do like this, but outside that meh.
Vital Spirit / Insomnia: Immunity to sleep is pretty big
Anger Point: again +6 from a crit is nuts
Own Tempo: Immunity to confusing ain't bad, with hurricane everywhere and Machamp in UU, I could see it's use
Color Change: I think this needs more discussion
My thoughts:
Imposter: S Tier - Abilities that are so good that the ability will often make otherwise unusable Pokémon viable. It doesn't matter that things that already have strong niches without it and wouldn't be able to fill them with it, it's a good enough ability to turn pretty much anything in NU (outside maybe Shedinja and possibly a few others) into a deadly OU viable revenge killer.
Moody: I agree with you that Moody is a broken ability, but, once again, I go back to the S Tier definition. Sure, Moody may be the best S Tier Ability, but it still falls under the definition.
Flower Gift: Flower Gift actually works on both the holder of the ability and its partners, so it actually is useful in singles. I think whether a single boost in Attack and Special Defense in sun is worthy of A Tier could use some discussion though.
Analytic: I kind of agree with you that we definitely haven't seen Analytic distributed to anything that can or wants to abuse it to its full effect (and I agree I see the value in a discussion here), but I can still also see the argument for leaving it where it is. One of the ways we're supposed to be able to distinguish B Tier abilities from A Tier ones is that they require a more specialized stat spread. Analytic becomes less effective the more speed you have, and requires the bulk necessary to take the hits required for something that wants to go second. Also, this is just theorymoning but walls are also generally slow, so the things that you're going to be hitting harder are the things that are less bulky (of course this might be a bit different if the boost activates on switch outs, which I don't know if it does)
Shed Skin: I think a discussion is worthy here as well. The moveset data isn't up anymore in the usage stats, but about half of all Scrafty run Shed Skin despite having the A Tier ability Moxie. It comes down to how valuable you regard a 30% chance to be cured of status each turn, which in itself isn't that high, but rises to 51% over two turns, 65.7% over three, 75.99% over four, 83.193% over five, etc.
Infiltrator: I can see the point of a discussion here. I believe it comes down to how common one regards screens as a component of used strategies. If they're common enough, I could see the reasoning for putting it in B, but, if not, I believe it falls under C's mentioning of niche uses.
Inner Focus and Steadfast: Sure flinch isn't the most common thing, but with Jirachi on over 15% of teams, shutting down its paraflinch set for the most part is still a good niche to have. That's really all its good for in OU though outside of uncommon things.
Pressure: I could go either way on this one. It really depends on how valuable and large a niche you view stalling out low PP moves as
Iron Fist: Sure they do, but the boost is small, only equal to that from Expert Belt or the Elemental Plates. I'm not sure where to go here, but that should be taken into account along with the small number of moves that are boosted by it.
Pickpocket: Yeah I don't think this is that great an ability. Outside gimmicky gem sets, sash mons (maybe; does it work if sash was just consumed?), or berry sets you can't run an item to use it to its full effect, and would probably be better off running your own than stealing one from your opponent.
Vital Spirit / Insomnia: I actually have come to agree with this potentially needing a move. This is especially true because immunity to a status is, in my opinion, more useful more of the time than immunity to stat drops (Clear Smoke and White Smoke), an attack boost after stat drops (Defiant), dealing a little damage if your opponent is asleep (Bad Dreams), etc. Unfortunately, the rules of this phase of the discussion forbid voting on both Insomnia & Vital spirit and Defiant and Bad Dreams, so I'm not sure what we can really do about it.
Anger Point: Crits only happen 5% of the time though. Plus, the crit needs to be weak enough to not KO you. That seems in line with the "abilities [that] may come in handy once in a blue moon" in the D Tier description
Own Tempo: Pretty much what I said about Vital Spirit & Insomnia
Color Change: I don't feel strongly enough to state an opinion here. I think it's a bad ability, but I'd like to here what other people have to say.
On to my things I want to talk about.
1.) All of the status immunity abilities are C Tier while all of the big stat drop immunity abilities (including essentially Defiant since the only thing it's going to do that often is reverse Intimidate) are B Tier. As I mentioned earlier, I don't know exactly what to do about this since Insomnia, Vital Spirit, and Defiant are excluded from voting during this phase.
2.) Solar Power. I brought this up earlier and people dismissed it arguing that (a) the HP drop of 12.5% occurs very quickly and independently of whether your attack connects, (b) that only super powerful special attackers or ones with fire STAB could take advantage of it since anything else would die to easily against resists, and (c) that life orb is superior (as it’s not sun dependent) and you can’t run both effectively. I pointed out that (a) if you were worried about the HP drop you can run leftovers and live 16 turns (as opposed to life orb’s 10 attacks) and longer if you happen to be in when they change the weather, (b) if you’re worried about power, running specs on something with solar power gives anything with more than 53 Special Attack has more power in sun then itemless Deoxys-A, meaning anything with even decent Special Attack is going to be very powerful, and (c) that, while Solar Power may give only 1.15x more power than Life Orb, Specs Solar Power gives 1.73x more power, which is not at all equivalent. I’d also like to quote a point I raised comparing it and guts: “from my perspective the ability either makes you less frail than guts does (since you can get the boost even if you're running leftovers and will thus last longer than something with a status orb) or is more reliable than guts is (since you can control to an extent whether the sun is up but cannot control whether you're statused if you don't run a status orb).” Maybe there are other reasons not to move it to A tier or there are flaws in my reasoning, but I’d like to see them so this can stop bothering me at least.
That’s it for now, maybe more later.