Aight so me saying Aegi makes certain pokes 'unusable' is technically incorrect, lemme rephrase: The existence of Aegislash makes other pokemon so shit in the mega that nobody wants to use them anymore. Because I feel it's worth mentioning, here's some good-but-currently useless pokes that will cry sweet jesus tears of ecstasy once Aegislash is gone (although pretty soon I'm gonna have real-life shit to do so it'll be incomplete but I might update if relevant):
Spinners:
Starmie over here will relish the loss of Aegislash. In fact, the main reason Starmie has fallen so drastically in usage is because it can't beat Aegislash. Yeah the Defog buff hurt her too, I'll give you that, but even before the sand craze Starmie was being tossed aside for Excadrill b/c despite being faster, having access to the BoltBeam combo, Scald, and Psyshock to beat stuff like Amoonguss and Mega Venu on the switch, two great abilities in Analytic and Natural Cure, and longevity in Recover, that all didn't mean jack shit with Aegislash around, cuz Exca is the only spinner bar maybe Mega Blastoise (ew) that stands a chance of beating the Slash.
Forretress isn't as good as Starmie this time around, I'll give you that, but it still has several redeeming qualities. Titanic physical defenses don't hurt, neither does access to literally every form of entry hazard bar sticky web, nor pivoting abilites in Volt Switch, and a strong Gyro Ball is nice. Plus EQ doesn't hurt for surprising Heatran on the switch. Sturdy is also much appreciated for when you need that extra layer of spikes or those rocks off the field before going out. Forretress has a shitload of utility, and while Wish Support is greatly appreciated, it can still do a good job of setting up rocks or keeping them off when need be. Albeit, bar Rapid Spin it's pretty much outclassed by Ferrothorn, but it still has a respectable niche as a spinner. Or it WOULD, rather, if it stood a snowflakes chance in hell facing up against the most common spinblocker in the game (hint: it's Aegislash). The amount of damage Forretress' EQ produces is enough to 2HKO Excadrill while Adamant Exca only 4HKOs Forry, but the damage it does to Aegislash is laughable, at which point it proceeds to KO you with Shadow Ball. A spinner that can't beat Aegislash is, at the moment, a useless one, and the fact that it can beat the most common spinner 1v1 means absolutely nothing.
Walls
(only one I can really think of atm)
Bronzong is a pretty damn good poke, but you'd never know that seeing as how it didn't even make the OU viability ranking list. The steel nerf really hurt Zongers, only capitalized upon by the existence of Aegislash. It has two great abilities in Heatproof and Levitate, with the former possessing the ability to beat Heatran with EQ 1v1 and the latter being able to handle shit like D-nite and non-Fire Blast Garchomp no problem. Depending on the spread it can even survive a LO Gengar Shadow Ball and proceed to murder it with Zen Headbutt. This fucker's guaranteed to get rocks up, and if you don't play like a total scrub this thing will last well throughout the match despite having no reliable recovery bar Rest and Lefties, and it can actually pull its own weight against a large portion of OU, especially when supplied with excellent teammates (see: Mega Amph). But it can't even touch Aegi, so sorry Bronzong, you don't get a rank. Yes I am aware Bronzong is outclassed by stuff like Ferro but Aegislash is the reason it's almost nonexistent anywhere in OU.
Misc.
This is a fucken sin right here. Toxicroak's usefulness diminished with the rain nerf, but it still has plenty of redeeming qualities. It has FOUR great boosting moves in Swords Dance, Bulk Up, Work Up, and Nasty Plot, priority in Sucker Punch and Vacuum Wave, access to great omoves like Knock Off and Drain Punch, and looks hella dope. His typing and ability in Dry Skin are also superb, allowing him to offensively check Azumarill and Bisharp, offensively and defensively check Crawdaunt, defensively check non-HP Flying Keldo variants, murder Chansey, and after a few boosts his dual STABs can plow through a good portion of the tier on their own while Sucker Punch can oftentimes handle the rest (Gengar, Lati@s). He does need some support, but provide it properly and he can do quite a lot with his large range of versatile sets to choose from. His stats are kind of shitty, but he's got the movepool to compensate largely for it. Oh wait, I forgot -- Aegislash exists, which Toxicroak literally can't touch with many sets and hardly leaves a dent in others, and at this point is more trouble than he's worth. Sorry Toxi, C- for you.
I'm done for now, I spent too much time typing this up and I should go outside or something. Also, as I'm sure people will love to chime in,
SO HERE READ THESE BOLDED COLORFUL LETTERS, I HAVE YOUR ATTENTION YES? Good, so be aware that I understand that there is much more than just Aegislash this gen keeping these guys from rising too much in the ranks, like Talonflame and Mega Zards and other scary stronk stuff out there, but none of them have affected these mons as much as Aegislash. So please, let us join hands and ban Aegislash. Do it for Rapid Spin. Do it for sentient rain bells. Do it for Toxicroak.