There are some special secret and hidden items/weapons in the game. Here are their locations.

Rapier: Visit the house in chapter 2 located in the middle of the forests with Shon.
Emblem Lance: Visit the house as mentioned above with Gordon.
Elysian Whip: Bottom of chapter 3 where the Pegasus Knights are.
Talisman: Enter the odd, empty room located in chapter 5 with any unit.
Killer Lance: Defeat the cavalier holding a Killer Lance in chapter 5x.
Member Card: Talk to Tekun with Althares in Chapter 15.
Guiding Ring: Have Kelik or Anakin step/wait to the right of the pillar in the Respite from Battle.