Shadow: Anything before November 1st, 2018. Knuckles being an AT. Shadow being absent as an AT. Grinch Leak didn't help things much, either. This is the one I'm the most upset about to this day - at the very least he could have had an echo. You give it to Ken and Richter, but not Shadow, the most iconic "clone" character?? Always struck me as odd. Complete missed opportunity.
PMD Grovyle/Sceptile/Grass-Type Pokemon: Smash 4, for sure. This one hurts. So, we got Greninja as a water type, and Charizard on it's own as a fire type. We just needed one more to fill out the fire-water-grass trio. During the Smash ballot days, people rallied behind Sceptile - ORAS was brand new at the time, and the most popular grass type at the time was Sceptile. It got a prominent role in the XY anime as Sawyer's ace, akin to Ash's Greninja. It got a mega evolution. It was this close and... nothing. We didn't get any new Pokemon during the ballot days.
Then for me, this changed over to Decidueye, and now Rillaboom. I like grass types, and Ivysaur doesn't cut it for me. I'd happily trade Incineroar for Sceptile any day. Don't really know why anyone is clamboring for yet another fire starter (Cinderace) when we sorely need a grass type. That's the one pick that would upset me the most, I'm completely fine with any other rep except from Cinderace.
As for PMD Grovyle, I loved him from those games, and it'd be nice to see PMD get representation - the bonus episode in Explorers of Sky made me tear up. Great story-telling there. Primal Dialga's theme was robbed. No idea why that song isn't in Smash yet. Either way, the Treecko line is one of my favourite starter lines, and it's sad to see them just.. not there. Their highest chances was with Smash 4 and ORAS, but it just didn't happen. Shame.
Geno: Unironically him surviving seven Mii Costume waves in a row, when realistically he would come back with Hero. Just the fact that Geno's Mii costume didn't come back with Hero is enough for me to think "He has a shot this time, I know it". It's odd that his Mii costume's still missing, along with Chocobo's. It's easy money for Square, why not add them for Hero's pass?
Rayman: Artsy Omni. But we got suckered there. I didn't believe the "Rayman is under the ice" stuff, always struck me as silly. I'm not sure why he's not in already.
Dixie: Echoes being announced. I really do not want to see Dixie as an echo, she deserves much more than that. She is more than a "Wig Diddy". But if that's what it takes to get her, then whatever, I'll accept that.
Shantae: The Smash ballot. Especially when WayForward was really vocal about her, especially her color alts. I remember them showing those off.
Master Chief: Everything prior to Steve being revealed. Things were looking up for the Chief, I and several others knew Microsoft wouldn't single-dip - they want more in Smash. That turned out to be true with Steve, although there was a lot of evidence pointing towards the Chief instead.
Neku: Smash ballot again. After Cloud, Square Enix being represented was finally a possibility. Neku's game was a cult-classic on the DS, it was one of the games you bought a DS for, it was that good. TWEWY was mostly on the sidelines, akin to Chrono Trigger or SMRPG for a good while, until about 2012. It got a sudden revival. From there, it got a release on Android/iOS in the form of Solo Remix, it got prominent appearances in Dream Drop Distance, and then it also made appearances/references in Kingdom Hearts 3.. and then the Switch version of TWEWY came out - more content after the ending. New visuals.
From all this, I'm pretty sure you could tell Neku had high hopes this time around. When I voted for him on the Smash Ballot, his DS game was all he had - just a niche, but cult-classic of a game. Now look at what he has now.
Edit - IMPA! Forgot about her. I loved HW and I thought that game had the best designs yet - especially Impa, who's always looked off in some way. And she was another Zelda character. And she played so differently in comparion to say Sheik. So I rallied behind her too. She didn't happen, but it's funny how we still got a two-hander in the form of Cloud - seeing as Impa's one in HW.
I'm happy to see her get a revival in speculation because of AoC. She looks great, but it definitely feels like history is repeating for me. I desperately want HW to get representation in Smash. I wanted HW Impa. I wanted Linkle, I love her design too - she has dual crossbows, how cool is that. I wanted her playable in the mainline Zelda games. I wanted HW skins for all of the triforce trio. It may be a spin-off, but it's still one of my favourites in the Zelda franchise.