Aeris's outfit mainly, and her Guard Stick to go with it.
Really if the FFVII event is going to go ahead, I think we're just going to get FFVII themed weapons, and this is my best guess for what class get's what (I've had to do a bit of creative embellishment for some, as some weapon types used in FFXIV simply do not resemble anything in FFVII):
GLA/PLD: the Enhanced Sword Zack used for most of
Crisis Core (that Cloud also used), along with a Shinra riot shield labelled 'Shinra Alpha' which was an armour type in FFVII.
CNJ/WHM: Aeris's Guard Stick as mentioned, or else her Princess Guard or Umbrella!
THM/BLM: Aeris's Wizard Rod or Striking Staff
LNC/DRG: Cid's Venus Gospel or Mop
PGL/MNK: Tifa's Leather Glove or Premium Heart
MRD/WAR: Cid's Mast Axe or Viper Halberd
ARC/BRD: Cait Sith's Megaphone or Marvellous Cheer (reimagined as a bow with the horn of the megaphone the arrow quiver!), or else Minerva's Bow from
Crisis Core
ACN/SMN/SCH: Red XIII's Limited Moon (reimagined as a book, much like how Hope's FFXIII weapon was a 'book' here in FFXIV)
ROG/NIN: Yuffie's Twin Vipers, reimagined as twin blades
MCH: Vincent's Cerberus from
Advent Children and
Dirge of Cerberus, as the name for both his starting weapon and ultimate weapon are already in the game (Quicksilver is a lvl 50 MCH gun and Death Penalty is the name of one of Merlwyb's pistols)
AST: Barret's Missing Score, believe it or not, reimagined as a star globe (the Missing Score had an angel wing motif on it and the 'score' in the name does suit a card deck)
DRK: NOT Cloud's Buster Sword (as that is already in the game as the lvl 1 and 2 melee DPS Limit Break), but instead Cloud's Hardedge from FFVII, the Ultima Weapon from FFVII, or his 'First Sword' from
Advent Children
SAM: NOT Sephiroth's Masamune, as I'm certain SE are carefully keeping that in reserve for later inclusion in the game (given it's a reoccuring weapon throughout the series), so instead, either Cloud's Yoshiyuki or Murasame blades.
RDM: Genesis's rapier from
Crisis Core (as the name is unknown perhaps calling it 'Loveless Rapier' or 'Genesis's Rapier'?)
BLU: Aeris's Aurora Rod
GNB: the Velvet Nightmare gunblade Kadaj and the Remnants used in
Advent Children
DNC: Yuffie's Conformer, reimagined as a pair of chakra.
But I'd be happy as long as I got Aeris's outfit (dress, jacket, bangles, boots and hair ribbon-complete-with-white-materia

).
