Here's a topic about all the little hidden references to other games and trivia for FFXII. First, a couple things I've noticed and/or stolen from wikipedia:
1. All of the espers in this game are either Zodiac Bosses from Final Fantasy Tactics, Totema from Final Fantasy Tactics Advance, or bosses from Nintendo-era FFs.
2. Gilgamesh wields swords from past FFs. His arsenal includes:
-Cloud's Buster Sword (with the kanji for "Replica" on it)
-Squall's Gunblade (with a Chocobo on it)
-Zidane's Orichalcon
-Tidus' Brotherhood
-Odin's Zantetsuken
-Excalibur and Excalipoor
-Loto's Sword from Dragon Warrior 1/3
3. Montblanc is from Final Fantasy Tactics. (obvious)
4. Balthier has the same last name as the Final Fantasy Tactics characer Mustadio, another gun user.
5. The clan rank "Riskbreaker" is a reference to the game Vagrant Story. Ashley Riot, the main character of Vagrant Story, was a Riskbreaker.
6. The Zodiac Spear and Zodiac Escutcheon are no doubt references to the Ultimate Javelin and Golden Escutcheon from Final Fantasy Tactics. These being the strongest weapon and strongest shield in FFT. Both were one of a kind weapons found by using Move-Find Item in a one-time only battle.
7. FFXII is the sixth game to ever receive a 40/40 from Famitsu magazine. It is the first Final Fantasy to do so.
8. Yasumi Matsuno was the original writer and director of FFXII. He also created Final Fantasy Tactics and Vagrant Story. He worked as producer for Final Fantasy Tactics Advance.
9. Yasumi Matsuno is the only man other than Shigeru Miyamoto to have created two games that Famitsu has given a perfect score. These games are FFXII and Vagrant Story.
10. Bloo, from Foster's Home for Imaginary Friends and Basch share the same voice actor, Keith Ferguson.
11. Judge Zecht is voiced by Phil LaMarr, better known for providing the voice of every animated character ever made.
12. Migelo and Gilgamesh share their voiceactor: John DiMaggio. Better known as the voice of Bender.
I can't think of anymore, and I don't feel like trolling through the VA lists. Anyone find anything else?