OK, this has been going for a week now, so I'm going to reveal the answer. I give the next riddle to §håd0w as he was the closest.

Defeat the ultimate to get the same, (Defeat Ultimate WEAPON to get Cloud's Ultimate Weapon)
Hunt, discover, and spend, (You need to hunt down enemies that drop the items needed to customise Squall's Lionheart)
Riding on a bird near the bubbling transporter, (You find Zidane's Ultimate Weapon by using a Dead Pepper while on a chocobo near the Shimmering Isle bubbles)
Travel to the beyond, then return to the place of tranquility,
You will find me there.(You need to go to The Beyond to get Tidus' Sun Sigil, then go to the Calm Lands to get his Caladbolg)

So the answer was the final weapons from FFVII - FFX.