Several entries in the Chronicles (or Brave Story, if you're playing the original PS1 version) are technically used, but unable to be seen in normal gameplay, as these entries are only added after crossing the Point of No Return, after which viewing the Chronicles is impossible.
The Japanese release contained the Zodiac Brave Story Sound Novels, a collection of four mini-games in the style of Choose Your Own Adventure stories. Because of time and budget constraints, they were never translated and left unused in the non-Japanese versions. This in turn leads to some technically used musical tracks to be Dummied Out of non-Japanese versions as well, though unlike the sound novels, the tracks can at least be listened to in the Sound Test of the PSP version, along with several trulyDummied Out tracks.
A good chunk of text is left out of the game, mostly battle classes (and their descriptions) of characters who are normally scarcely, if at all, seen in battle. Notable strange cases include Delita's Sis (Tietra), Bishop (Simon) and Phony Saint (Ajora).
There were originally going to be twelve Knights Templar, and Matsuno even wrote names, genders and ages down for them.
Likewise there were originally going to be a full lineup of thirteen Lucavi, one for each Zodiac Stone. The names of the main twelve (ie excluding Bonus Boss Elidibus/Zodiark) are listed in Ivalice script on the Zodiac circle shown in the background of the save screen, though the six who did not make it to the final game had their names Retconned by Final Fantasy XII.
One of those demons was going to be called Rofocale. This name was later used for a zombie enemy in a map where he tries to take the Zodiac Stones from you.
It's speculated that Valmafra (Balmafula) was supposed to have a greater role in the game, and was likely to be either a guest or a recruitable character at some stage in the game's production. She even has her own Battle Classnote Witch of the Coven/Arc Witch, it has a description but no assigned abilities, yet never once appears on the battlefield.
Dummied Out sprites and lines of text suggest that a handful of other characters were meant to be recruitable, or at least guest characters. Aside from the aforementioned Valmafra, such sprites and text exist for Oran, Simon, and even Tietra. The latter two have battle classes of their own (Bishop and Delita's Sis respectively), and Simon even has a full set of battle animations despite never even being seen in battle at any point. Tietra has another oddity; when hacked into the roster, a strange sprite, left unused anywhere in the game, is used as her menu sprite.