General Information Topic
This is a list of classmarks that are not easily acquirable. I have excluded buyable ones and ones that are given to you as a part of events, since those are easy to amass.
Magus Classmark (Warlock/Witch): Dropped by and stolen from Warlocks/Witches, very rarely. Several bosses, such as the Magus Gildora, have much higher chances of dropping it.
Necromancer Classmark: Dropped by the necromancer on the 18th floor of the Palace of the Dead, but only if you've recruited Cressida.
Vartan's Classmark: Dropped by multiple Hawkmen in Chapter 1.
Hagia Knight's Classmark (Knight Commander): Dropped by Oz and Ozma at level 32+. Ozma won't drop it in the lawful route however.
Also can be stolen from a zombie Templar Knight, encountered only when its raining at the Vanessan Highway. Ozma must be already recruited.
Abuna's Classmark (Priest): Stolen from clerics in Phorampa Wildwood.
Heretic's Classmark (Dark Priest): Dropped by the cleric on the 8th floor (Enraptured Dreams) in the Hanging Gardens, as well dropped by the cleric Templar Knight on the final floor.
Pirate's Classmark (Buccaneer): Dropped by the white skeleton encountered on the map 'On Holy Ground' within the Pirate's Graveyard.
Additionally you may get one by taking the pirate's treasure at the end of the Azelstan's sidequest.
....on second thought I'll leave this one alone. Maybe later. >_>
SIGH. I'll do this one later.
Upon clearing the game you will unlock the World Tarot system, an interesting new feature that allows you to go back to certain 'Anchor Points' spread throughout the game. This lets you to replay parts of the game at will, and more importantly make different decisions to play out the different routes of the game.
Nearly everything is kept while using World, including characters, levels, items, and money. The only things not kept are Chaos Frame and the Warren Report, which will remain consistent with that 'timeline'.
Special characters are kept, and will be forcibly deployed in story battles where they are present as guests.
It is possible for many special characters to face themselves in battle as well, with no repercussions. However, special characters may remain flagged as dead in other timelines (if that was their fate), so scenes will not inappropriately trigger if it would not 'normally' be possible within that route. The exception appears to be to start The Search for Warren, where apparently its possible to do it in the Neutral route even though a certain prerequisite character should be dead in that route. (Confirm?)