Flawless Execution is handy against the likes of The Dreamer, as it effectively functions as a universal damage boost, unlike KNYFE's damage boosting equipment.
This amuses me, since that's one of my favourite AA cards. I'm much less likely to play Scherzo of Frost and Flame; 2 damage is fine, but not compared to a lot of what AA can do.
I feel the same, but today I played with a new player (their second game), they took Ra and really liked this card. Different strokes, I guess.
Sucker Punch, Wrathful Gaze and Suture Self are ones I would add.
Oh, huh. I forgot Wrathful Gaze even existed, which I suppose goes to show how often I use it.
That discussion of Punish the Weak was exactly the sort of thing I was looking for. :3 I always use it, for those times when you need a good Rampage. Plus, the debuff isn't so bad with Taiaha, if there's no DR on the villain targets.
I definitely have to try Self-Sabotage on Omnitron now. That just sounds totally unreal, I'm going to have to see it to believe it. 
But yeah, I usually ignore that and Singularity until I realize, hey, there's more equipment cards on the board than the villain has HP!
It's funny, re: Rhapsody of Vigor, I adore that card ("Heal the bots! D:" "Heal the Dreamer! D:") and find that Scherzo is my last choice with AA. Fanatic-style damage is nice, but he's almost never got a buff to make use of it when I need it. Scherzo is only for when ARGIE MAD! ARGIE SMASH!
Also funny is Superhuman Durability. In theory a great card, but it seems like I either never get hit with that much damage once it's out, or else I've got Shielding Winds anyway.
And this. It would be great on literally anyone else, but usually AA is struggling to not die. I can only see it being useful for when you've got all your instruments out and it's time for a grand finale, the kind where you're gonna burn both your Alacritous Subdominants and just do everything.
I remember 1 game where we were facing Akash'Bhuta and as AA my opening hand contained 2 Scherzos and Pipes. The first 2 environment plays were both Obsidian Field. By round 3 AA was doing 16 damage a turn!
Mists of Time is a card I don't use. Even when flipping her deck might be a good play I typically have better ones.
It works great with salvage yard though!
Thats a good one I saw posted elsewhere. Most times though it does not seem the best play.
The only time Mists of Time is really a useful play is when most of your deck is in your deck, and you are ready with Mist-Fueled Recovery the next turn. So, it's rarely useful. On the other hand, it has 3 and 4 as its spell points, so it still has value even though it's rarely playable.
I stack the trash with 4s (maybe 3s) then after a bit switch the decks and just unleash for a few turns.
So yeah, I tried this, against Cosmic no less, and oh my god, it's one of the most psychotic interactions I've ever seen in this game, 100% unfair and hilariously awesome.
Plus, once Omni-X gets some of his own Components in play, Omnitron will never flip.
I don't use it often, but there are a couple of situations it comes in handy:
(1) Villains who don't put out targets themselves. (Spite, Iron Legacy, Plague Rat come to mind). Unless you're playing in a target-rich environment, a lone villain will almost always be the target with the lowest HP, so it's effectively a +1 DMG for Haka.
(2) Overcome Damage Reduction: It can help to take out pesky things like Voss' Gene-Bound Guards, Citizen Truth, and Gloomweaver's Disciple (forget his name) that does -1 DR – they're all low-HP targets, so will likely qualify for the +1 DMG.
(3) Feed Ongoing Destruction: If you're dealing with villains that like to destroy ongoings, having it out there to sacrifice to keep your more valuable ongoings from getting killed, or as food for DW Fixer's power.
I don't use Sky Scraper's Explosive Reveal. I think I have only ever used it once.
I don't know how many people will get the reference, but; with Punish the Weak and Savage Mana, Haka is the equivalent of a "Carry" in DOTA.
WIth these cards, you encourage a playstyle of taking out many low-HP targets, and getting the finishing blows when others have weakened them, building SM up faster than you otherwise would. Place Haka late in the team order, get other party members to wear enemies down, and give Haka the last hit.
Keep in mind that the "lowest HP" check is applied to each target at the time you damage them; if you're attacking multiple targets, hit the lowest HP one first, and destroy them, a new target is now the one with the lowest HP and PTW will give that boost against them too. In certain cirumstances (especially against villains heavy with many low-HP targets, like Omnitron), PTW and careful ordering can be the difference between leaving everyone alive, or wiping everyone out (and getting a big Savage Mana boost to boot). When Savage Mana does fire, you generally do so much damage that the -1 damage for hitting a none-lowest target (assuming you haven't clear the rest of the board in advance) will be negliable anyway.
I always WANT to use it, but then at the time it’s in my hand I either don’t have many links in play or I would rather have the links in play.
In one of the very first games I plaed of Sentinels, I was playing Haka vs. Voss and I played Punish the Weak to improve my ability to stomp all over his minions while the other players focused on bigger targets. I don't play it often, but it does have some use.
My friend and I call this the "janiotor Haka" build
Superhuman Durability's effectiveness, as other cards like it depends a lot on H. With 4 players or less it's rarely useful, but with H=5 and some villains, it's very useful. In the same way, Undaunted gets very powerful in many H=3 fights.
Enduring Interecession is a card I play often. Haka may lose a lot of hp, but other members of the team are fine and can fight far longer - and Haka of Restoration means you can endure even longer. In fact, Haka is very good at handling environment's with lots of targets, thanks to Enduring and Punish the Weak, letting everyone else take care of the villain. Until Haka finishes with a big savage mana fueled by all these environment targets.
Excavation allows Ra to draw up to three cards. The only way he can have extra draws outside of Summon Staff.
Prayer of desperation is incredibly useful after using Divine Focus for a full round, or even Wrathful Retribution : lose a turn to go back to a full hand.
I recently learnt to play Nightmist with no Talisman, using her other powers. It's a very different Nightmist, less destructive, but very good at controling, both the villain and her own deck. I spend far less time waiting for a talisman now that I am used to having her do other things.
Drawn to the flame is my favorite Ra card : with the Staff, you can deal 1 damage to every target even if the villain has no ongoing. Add imbued fire and solar flare for maximum destruction. And if the villain has ongoings...
Coolant Blast is only effective if you can be sure to drench AZ in flames. When he is in team with Ra, AZ often becomes the main target of Ra's damage... In some environments or against some villains, it's good single target damage - even if you dont have modules in play.
I like Mass Levitation a lot. It neutralizes most of environments, and life is easier when you don't have to worry about all that damage.
There are less and less cards I never use - last year I decided to "force" myself to play all cards I didn't find interesting and see what happen, and they are all very surprising.
Living Conflagration?
I actually got a lot of good use out of Punish the Weak while trying to unlock Heroic Infinitor. It basically negated his damage reduction.