Newcomers:
's Secret Ninja Attack - Part of this could be my bias for Greninja speaking, but I just love how it captures Greninja's ninja nature very well with the darkened setting and his fast movements. The moon in the background and Greninja's rapid cries with every slash makes the Final Smash feel even better, to the point that it feels really satisfying when Greninja delivers a KO with the finishing strike.
's Pair Up - I love it because it's Chrom's time to shine, and seeing him beat up the opponent like that feels satisfying to watch, especially for a Chrom fan who felt hurt because of the way he was deconfirmed.
's Infernal Climax - I really like the Danger Zone effect involved. In any moveset I can think of for any character, never did I think about an effect like that until Bayonetta came along, and it's pretty good idea that I hope we'll see happen with future Final Smashes. It's got an interesting way of executing the attack with the whole "attack your opponents as much as you can to fill the gauge", and the result? Gomorrah violently chomping on the opponents and finishing it off with a menacing roar. Just the very nature of Gomorrah's vicious voting fits really well for the final DLC character. It demonstrates what a Final Smash is really meant to be: a vicious and powerful attack that is designed to finish your opponents!
's Mega Legends - How can you say no to this one? The fact all the Mega Men throughout the Mega series appear alongside Mega Man to deliver the ultimate lasers of doom looks insanely epic!
's Staff - Yes, it's the same as Zelda and Sheik's Final Smash, but it is far cooler. The way Dark Pit says "Goodbye" sends shivers down my spine, yet it makes landing a KO feel much more satisfying.
Veterans:
's Galaxia Darkness - One of my favorite Final Smashes in Brawl. The darkness setting down when you catch the opponent as Meta Knight utters the word's "Behold" or "Behold my power", followed with the powerful slash, makes the Final Smash feel bone-chilling yet awesome at the same time.
's Psystrike - If there's a Final Smash that screams "dramatic", this is the one to do so. Mewtwo Mega Evolving, then unleashing a huge ball of energy that causes any opponent caught to become stunned (as if Mewtwo is messing with their brains) when it makes contact with them, and then unleashing a blast of psychic energy that delivers strong damage and knockback (which can also KO exceptionally early compared to other Final Smashes), good lord, this Final Smash is crazy I tell you!
's Blue Falcon - Another one of my favorite Final Smashes in Brawl. I like how it captures Captain Falcon's favorite hobby to take out the opponent. When the opponent gets up in the middle of the raceway after being caught and seeing the Captain Falcon piloting the Blue Falcon piloting the Blue Falcon directly in front of them, you know it's not going to end well for the opponent. I also like the addition of the F-Zero starting line tune when the Blue Falcon is about to run over the opponent.