Creator's Favorite: Mr. Satan/Hercule. Toriyama admits that Hercule is one of his favorite characters and he gets a lot of focus in the Buu Arc. However, he's very popular (especially in the Japanese fandom, he's more of a Base Breakerin the west).
Fan Nickname: Mystic Gohan for his Buu Saga power-up, which was never given a name (although the recent videogames seem to be going with 'Ultimate Gohan').
Mirai Trunks to the future Trunks, just plain Mirai, "Mirai Briefs" in some fanfiction when he returns to the normal timeline and lives with the 'other' Trunks. Crosses with Gratuitous Japanese.
Kushami (Japanese for "sneeze") for Lunch blonde form, Ranchi (the Japanese approximation of "Lunch") for her blue-haired form. The first was coined in early manga summaries before the series was translated, and they are/were very, VERY common Fanon.
Majin Buu has several, depending on the people he's absorbed (the main ones being Buutenks/Super Buu 2, Buuccolo/Super Buu 1.5 and Buuhan/Super Buu 3.)
Frieza, his family, and his race as a whole, have been given the name "Icejins." They have also been called "Changelings."
What Could Have Been: Originally Gogeta was supposed to be in the manga, but because the writers behind Fusion Reborn came up with the concept before he could unveil it, Toriyama came up with Vegito instead.
Frieza was specifically created to be the Final Boss of the manga, but it ended up continuing. The same thing happened soon after: Cell was specifically created to be the Final Boss too, this time for real... but the manga ended up continuing again.
The FUNimation dub was their first major import, using hometown voice actors - everything they've done since mostly draws from this same pool.
In Mexico this went to a whole other level. Goku's voice actor is so very recognizable to the point where some people can't watch other dubbed shows (or movies starring Bruce Willis) without referring to a character as "Hey, that's Goku!".
Playing Against Type: Kenji Utsumi has it half and half when he plays Commander Red (no pun intended). Although Commander Red is nonetheless a military dictator, which fits one aspect of the roles Kenji Utsumi plays, he's also extraordinarily short, something that Kenji Utsumi isn't known to play as (he usually voices giant characters).