Mythics, broken down by whether or not they're worthwhile:
Conqueror : Easy 5-hit, Upheaval spam, WAR's best weapon in situations where AM3 can be maintained.
Glanzfaust : 30% Boost to Ascetic's Fury, which would probably make it Monk's best WS against really hard monsters (VWNMs). Probably not bad against hard content, but not awesome.
Yagrush : Useful for the same reasons it was always useful. Has additionally gained a melee-WHM use due to its Damage+30% on Mystic Boon (for MP recovery).
Laevateinn : Haters gonna hate, but this is the best Meteor staff by a LOT. The spell was freaking made to justify it.
Murgleis : Horrible. Death Blossom with +30% damage still doesn't really compare to CDC, which means this sword is only really useful in situations where you're able to maintain AM3 on melee RDM. Even then, you trade WS damage for DPS. The enhancement is stupid. It just isn't very good.
Vajra : It would be a decent offhand, does not strike me as a particularly useful mainhand. The Damage/Delay is terrible (53/200 vs. 55/176), which is really what screws this weapon, in my opinion. It relies on AM3 to be really useful (unless you're pretty much just using SA/TA), and Thief just doesn't have the TP-gain resources / Mandalic Stab sucks.
Burtgang : Eternal debate, best turtle PLD weapon, etc. Less of a debate now that they made its PDT pass the cap. Atonement is worse now than it was at 75, relative to the other options and considering a lot of ***resists it.
Liberator : Great in situations where riding AM3 is reasonable. Insurgency still looks like crap, but you could spam Entropy. The real reason this isn't getting a more enthusiastic endorsement from me is because Scythe doesn't give access to Resolution.
Aymur : Best pet-damage enhancing weapon, even without Aftermath. How much does Attack matter for pets? Not really known, but probably not that much. The Sic enhancement is kind of cool, but pet TP moves matter very very little. Damage+30% on Primal Rend probably makes it pretty good against melee-resistant enemies, but it won't compare to Ruinator.
Carnwenhan : Obviously extends the duration of songs quite a bit. After that it's a question of how much you care about extending songs as a bard. This would be okay if you really loved Bard, but it's not that good as a melee weapon (Mordant +30% is awesome, damage/delay suck and STR Thokcha probably beats it overall). 99 Carn makes it possible to maintain permanent Troub/Nightingale/Marcato buffs. Song duration with +5 Song type should be 10.5 minutes with all the proper gear.
Gastraphetes : Depends how large the Snapshot enhancement is. It hasn't been quantified. Overall though, this weapon appears to do nothing to address ranger's main problem, which is Enmity generation rather than damage. The Barrage Accuracy V thing is kind of a kick in the nuts, too. AM3 on ranged weapons is almost certainly not worth activating.
Kogarasumaru : SAM's best weapon when they can keep AM3 activated. Rana to activate it, spam Shoha. It's okay as a "tanking" GKT, but we left the balanced zone of 75 where ***didn't outright one-shot people that were prepared. Now you're either running with enough buffs to survive a monster or you're dead. An extra anticipate or two isn't going to change anything.
Nagi : "Tanking" Katana, but the damage/delay are pretty bad and NIN has never really excelled at melee "Tanking" hard things. Also, giving up their best Enmity tool (Blade: Hi) and quite a bit of DPS in exchange for 30 Enmity that will let them cap Enmity a little faster really isn't worthwhile. This is one of if not the the worst mythic(s).
Ryunohige : Awesome when you can keep AM3 up. Still honestly a pretty good option if you can't. Base damage -8 for WS damage+30% would be worth it, so see-ya Gungnir. This looks like Dragoon's best polearm in almost every situation.
Nirvana : Great Perp staff, solid boost to Avatar magic BP damage (though people tend to overstate this, it's like +25%). If you really love Summoner, I could see getting this staff.
Tizona : Tizona is a weird weapon. I'm still not sure if it's good or not, but I'm inclined to believe it is. Expiacion is unfortunately terrible even with damage +30%, but the MP draining makes sure that BLUs really just never run out of MP solo. Situations where that matters and situations where it's reasonable to keep AM3 up are mutually exclusive though, which hurts the weapon. I think it's worth having if you're a BLU4lyfe, simply because it's such a unique option.
Death Penalty : This one has probably taken the biggest fall from 75. Quick Draw Damage +60% is awesome, but Leaden Penalty pales compared to Wildfire even with damage+30%. AM3 on ranged weapons is almost certainly not worth activating.
Kenkonken : Easily one of the best Mythics. Stringing Pummel Damage +30% and Delay-50. It effectively has awesome DPS and the best WS damage. Not only that, but PUP doesn't exactly have a ton of other choices. This shits on Verth, and nothing else really matters.
Terpsichore : Damage +30% makes Pyrrhic Kleos better than Exenterator, but the damage and delay on this weapon are atrocious. It pretty much relies on AM3 to validate it, which would really only be viable in a few rare situations (playing support DNC). This is a weapon for a time that is long gone. But it looks like Raphael's sais, so I'm making it anyway.
Tupsimati : Sucks, sorry Scholars. Maybe SE will give you access to Meteor too so you can feel vindicated. It is pretty impressively useless otherwise.