I would like to see hacks for both the DS and GBA versions of the Mega Man Zero games that would restore the red blood from the Japanese versions to the American versions.
Kirby Super Star (Super NES): A hack that would add all the new content from the DS version to this version.
Mega Man 1-6 (NES): Hacks that would change the colors of all six games to be closer to the Mega Man 9 & 10 color scheme.
Rockman 7 (Super Famicom): A hack that is based on Zynk's English translation patch, but it would give all the characters and items their American names, doesn't change any of the sprites at all, makes all the English text upper case like in MM7 and it would change the word "Rock" to "Mega" on the title screen logo.
Contra Spirits (Super Famicom): A hack that would change all the text to English and replace the Japanese title screen logo with the American title screen logo.
Zombies Ate My Neighbors (Super Nintendo): A hack that would change the crucifix to make it look more like a actual crucifix and it would also change the one guy's sprite that appears in the credits level to his uncensored sprite from the Genesis version as well: http://www.hardcoregaming101.net/zamn/genheads.GIF
Pokemon Puzzle League (Nintendo 64): A hack that would change everything in this game to turn it into a N64 port of the GameCube version of Panel De Pon.
Splatterhouse 2 (Sega Genesis): A hack that would change Rick's mask to make it look more like the one he wore in the first Splatterhouse game.
Final Fight Revenge (Sega Saturn): A hack that would make Belger a playable character.
Sonic CD 2011 (PC): A mod that would add Knuckles and the Desert Dazzle level and final boss that were going to be added to this port but SEGA rejected them.
The Legend of Zelda: Ocarina of Time (Nintendo 64): A hack that would replace Navi's voice clips with Tatl's voice clips from Majora's Mask.
The Legend of Zelda: Four Swords Adventure (GameCube): A hack that would restore the missing content from the Japanese version back to the American version.
Mario & Luigi Superstar Saga (Game Boy Advance): A hack that would add all the new content from the Japanese version to the American version and it would also restore the unused Starbeans Cafe cameos as well.
Here's a video that shows all the new content they added to the Japanese version: https://www.youtube.com/watch?v=bDMXE10zeyQ
I would like to see someone port Bomberman '94 (The better version of Mega Bomberman) and Fire Pro Wrestling 3: Legend Bout from the PC-Engine to the Sega Genesis. I also would like to see someone port Dracula X: Rondo of Blood from the PC-Engine CD to the Sega CD as well.