This page so far contains info on each character's Sub-weapon, as well as which Karami-waza each character has access to and in which stances they can use them. To perform a Karami-waza, get close to your opponent and press back and X. If done correctly, you'll do a cool finishing move. I believe they can all be broken out of by mashing circle, though I haven't seen some of them escaped yet.
Note: The final two secret characters aren't listed because I haven't unlocked them yet. Will update once I have.
Sub-weapon
Iron fan, x1, non-lethal
Karami-waza
Katana - L, H
Nodachi - L, H
Longsword - L, M, H
Broadsword - L, H
Naginata - L, M, H
Sub-weapon
Knife, x2, non-lethal
Karami-waza
Katana - none
Nodachi - none
Longsword - none
Broadsword - none
Naginata - L, M, H
Sub-weapon
Sword, lethal, dual-wield with katana
Karami-waza
Katana - none
Nodachi - none
Longsword - none
Broadsword - none
Naginata - none
Sub-weapon
Sword, lethal, dual-wield with katana
Karami-waza
Katana - L, H
Nodachi - none
Longsword - none
Broadsword - none
Naginata - none
Sub-weapon
Sword, lethal, dual wield with longsword
Karami-waza
Katana - none
Nodachi - none
Longsword - none
Broadsword - L, H
Naginata - none
Sub-weapon
Sword, x1, dual-wield with katana
Karami-waza
Katana - none
Nodachi - none
Longsword - none
Broadsword - none
Naginata - none
Sub-weapon
Firecracker, x2, non-lethal, single use
Karami-waza
Katana - none
Nodachi - L, H
Longsword - L, M, H
Broadsword - L, H
Naginata - L, M, H
Sub-weapon
Shuriken, x2, non-lethal
Karami-waza
Katana - none
Nodachi - none
Longsword - none
Broadsword - none
Naginata - none
Sub-weapon
Needle, x2, non-lethal
Karami-waza
Katana - none
Nodachi - M, H
Longsword - L, M, H
Broadsword - M, H
Naginata - L, M, H
Sub-weapon
None
Can only use her rifle
Double-tap R2 to go prone, taunt with R1
Sub-weapon
Knife, x2, non-lethal
Karami-waza
Katana - H
Nodachi - L, H
Longsword - none
Broadsword - none
Yari - L, M, H
Sub-weapon
Knife, x1, lethal
Karami-waza
Katana - none
Nodachi - none
Longsword - none
Broadsword - none
Yari - L, M, H
Sub-weapon
Knife, x1, non-lethal
Karami-waza
Katana - none
Nodachi - none
Longsword - none
Broadsword - none
Yari - none
Sub-weapon
Frog, x1, non-lethal, scares all females except Tsubame
Karami-waza
Katana - none
Nodachi - none
Longsword - none
Broadsword - none
Yari - none
Sub-weapon
War cry, x2, non-lethal, opponent drops weapon
Karami-waza
Katana - none
Nodachi - none
Longsword - M
Broadsword - L, H
Yari - M
Sub-weapon
Card, x2, non-lethal
Karami-waza
Katana - none
Nodachi - none
Longsword - none
Broadsword - none
Yari - none
Sub-weapon
Knife, x1, lethal
Karami-waza
Katana - L, H
Nodachi - L, H
Longsword - L, M, H
Broadsword - L, H
Yari - L, M, H
Sub-weapon
Boomerang, x2, non-lethal, returns after thrown
Karami-waza
Katana - none
Nodachi - none
Longsword - none
Broadsword - none
Yari - none
Sub-weapon
Sword, x1, lethal, dual-wield with longsword
Karami-waza
Katana - none
Nodachi - none
Longsword - none
Broadsword - none
Yari - none
Sub-weapon
None
Can only use his revolver
Double-tap R2 to go prone, taunt with R1