I only really got into the genre this generation but I'll stick to characters that (I think) are new to this gens fighting game entries.
Ike (Super Smash Bros Brawl)
To my absolute delight my favourite Brawl newcomer also got given the heavyweight treatment, while Ike's not as slow as this in his game of origin "Path of Radiance" I can't say that i'm at all bothered at the liberties taken. Ike's Sword Ragnell is thrown around with such convincing weight, each impact landing with an incredibly satisfying wallop that blasts opponents wide across the stage. The moveset and playstyle does very well to differentiate from Marth who strikes with quick precise and maybe even elegant moves, Ike not being a lord of royal blood but a simple mercenary has this more wild and unruly style to his attacks and I really appreciate this contrast in sword fighting styles.
Each time someone says that he should be replaced by bloody Chrom in SSB4 they should get a Ragnell to the face.
Firebrand (Ultimate Marvel vs Capcom 3)
I'd like to say Phoenix Wright but then i'd be lying to myself no matter how amusing his attacks may be. Now the character that did work for me that I really wasn't expecting was Firebrand. Maybe part of the fun comes from the fact that no character I use quite pisses off my usual multiplayer opponent more but I figure there's a bit more to it than that, Firebrand's
brand *chortle* of aerial offence is kind of fun just to dick around with, numerous characters in the game can fly if need be yet this one really made me feel like the skies were my domain, at least in my piddly version of MvC3 fights.
Runner Up to Thor, mighty punish always makes my day.
Taokaka (BlazBlue)
Going through the original small roster for Blazblue didn't really have me click with any character except for this one. From design to in game mannerisms Taokaka jumped out at me with that unhinged nature that extended to the moves as well. I'm always one for claws on my characters and these are some hefty claws that's for damn sure. I can't help but feel that everything came together for me here, I mean even
her character theme is the best in my book, everyone else is rockin' out like super serious shit and i'm over here with this bizarre swing jazz thing.
Cerebella (Skullgirls)
As a wrasslin' fan I've always found it a bit odd that I never really enjoy playing as the hulking brutes that slam foes into the ground with exaggerated wrestling moves, perhaps grapple characters just aren't for me. Well until Cerebella at least, we're ratcheting up the comical absurdities of grapple moves here with a varied selection of delightfully brutal looking throws that can't help but make me smile. Cerebella herself has this satisfying "oomph" to her more standard striking moves, well as standard as they'll get in this crazy game and she has a fair amount of manoeuvrability for a grapple focused character.
I try using Viola in SC5 but boy does it end in disaster every time, curse you magic orb!
If we include pre existing fighters that were in games before this gen then Vega, Donkey Kong and Makoto (SF) are among my favourites.