Marvel vs. Capcom 2: New Age of Heroes (Arcade, Sega Dreamcast, Sony Playstation 2, Sony PlayStation 3, Microsoft Xbox and Microsoft Xbox 360): I want to see a hack that would do all this to it:
Balance the game out a bit.
Replace Bone Claw Wolverine with Norimaro.
Change M. Bison's name back to his correct name, Vega.
Make Roll and Servbot as strong as the other fighters in this game.
Give Juggernaut his Nail Slam move from X-Men vs. Street Fighter.
Give Charlie his Final Mission super move from Marvel Super Heroes vs. Street Fighter.
Give Chun-Li her Shichisei Senkukyaku super move from Marvel vs. Capcom: Clash of Super Heroes.
Have the Water Raft stage appear in Arcade Mode, only the ice version of that stage appears in that mode.
Modify War Machine's sprites so his armor looks closer to his official MVC2 artworks instead of looking like Iron Man: http://scrollboss.illmosis.net/comicedits/warmachine-capfgt_mvsc1_fistraise.png
Change Rogue's default colors back to her original green and yellow costume with the brown jacket and change the colors of her official MVC2 artworks that appear in the game to her original colors as well.
X-Men: The Arcade Game (Sony PlayStation 3 and Microsoft Xbox 360): A hack that would restore the original arcade voice tracks for all the characters.
Silhouette Mirage (Sony PlayStation): A hack that would restore all the content that got censored back to their original uncensored format and it would also change the gameplay difficulty back to it's original setting from the Japanese version as well.
Mario Kart Super Circuit (Game Boy Advance): A hack that would restore the original preview image of Sunset Wilds from the Japanese ROM to the American ROM: https://tcrf.net/Mario_Kart:_Super_Circuit#Regional_Differences
Maybe someone can hack Mario & Luigi: Superstar Saga and restore the missing Starbeans Café cameo appearances of random Nintendo characters with the Yoshi Magic tool that was just released on this site.