Previous weapons from the Final Fantasy 10 can be seen used by the characters in certain Dresspheres:

Brotherhood (Tidus): Yuna uses it when set to Warrior Dressphere.
Rod (Yuna): Set Yuna to White Mage Dressphere.
Long Sword (Auron): Set Yuna to Samurai Dressphere.
Caladbolg (Tidus): Set Yuna to Dark Knight Dressphere.
Masamune (Auron): Set Rikku to Dark Knight Dressphere.
World Champion (Wakka): Used by Tidus when he uses the Terra Of Zanarkand ability at the final battle.