Onimusha

Tips

 * Chests that require 'special keys' are for Michelle and can only be opened when you control her.

Vests

 * Blue Vest (Location: Forest)
 * Effect: Increases speed of enemy soul absorption.
 * Red Vest (Location: Sewers)
 * Effect: All souls become red, increase soul count.
 * White Vest (Location: Sekkai village)
 * Effect: Standing still recovers HP.
 * Yellow Vest (Location: Underwater Oni Temple)
 * Effect: Draw souls out of the enemy every attack.
 * Green Vest (Location: Notre Dome)
 * Effect: Draw souls and life out from living enemies.
 * Orange Vest (Location: Mont-Saint-Michelle)
 * Effect: Show enemy HP and Critical timing.
 * Purple Vest (Location: Mont-Saint-Michelle.)
 * Effect: Less magic power consumed.
 * Black Vest (Location: Critical Training)
 * Effect: All hits Critical.

EcoSpirits

 * Mt.Hiei: 2
 * Sewers: 4
 * Sakai: 5
 * Notre Dame: 6
 * Undersea Temple: 2
 * Boulogne Zoo: 7
 * Mont-Saint Michell: 9
 * Oni Temple: 1

Jewels

 * 1. SAMANOSUKE - Arch of Triumph - Power jewel (puzzle box)
 * 2. JACQUES - Mt. Hiei - Oni Jewel
 * 3. JACQUES - Mt. Hiei - Power Jewel (puzzle box)
 * 4. SAMANOSUKE - Sewers - Oni Jewel (puzzle box)
 * 5. SAMANOSUKE - Sewers - Power Jewel
 * 6. JACQUES - Senshuu Sakai - Oni Jewel (puzzle box)
 * 7. JACQUES - Senshuu Sakai - Power Jewel (puzzle box)
 * 8. JACQUES - Naban Ship - Power Jewel (puzzle box), Talisman (puzzle box)
 * 9. SAMANOSUKE - Notredame - Oni Jewel (puzzle box), Talisman (puzzle box)
 * 10. JACQUES - Undersea Temple - Oni Jewel (puzzle box)
 * 11. SAMANOSUKE - Undersea Temple - Power Jewel (puzzle box)
 * 12. SAMANOSUKE - Boulogne Zoo - Oni Jewel (puzzle box)
 * 13. SAMANOSUKE - Mont-Saint-Michel - Power Jewel (puzzle box)
 * 14. JACQUES - Mont-Saint-Michel - Power Jewel
 * 15. JACQUES - Azuchi Castle - Oni Jewel (puzzle box)
 * 16. SAMANOSUKE - Eiffel Tower - Oni Jewel (puzzle box)
 * DEFLECT CRITICAL TRAINING - Power Jewel
 * CHAIN CRITICAL TRAINING - Oni Jewel

Puzzles
 original Onimusha puzzle: .- 12 -.         |   .  |          8 dab  3 7 c.. 4         |  .   |          '- 65 -' unsolvable in 1 moves (4 moves attempted) unsolvable in 2 moves (20 moves attempted) unsolvable in 3 moves (84 moves attempted) unsolvable in 4 moves (340 moves attempted) unsolvable in 5 moves (1364 moves attempted) SOLVED in 6 moves (168 moves attempted): move: 2 .- 12 -.         |      |          8 da. 3         7  cb. 4         |  ..  |          '- 65 -' move: 4 .- 12 -.         |      |          8 da. 3         7 cb. 4         |  ..  |          '- 65 -' move: 6 .- 12 -.         |  a   | 8 db. 3         7 c.. 4         |   .  |          '- 65 -' move: 8 .- 12 -.         |  a   | 8 db. 3         7 c.. 4         |   .  |          '- 65 -' move: 1 .- 12 -.         |      |          8  ab. 3         7 cd. 4         |  ..  |          '- 65 -' move: 7 .- 12 -.         |      |          8  ab. 3         7  cd. 4         |  ..  |          '- 65 -' summary - moves: 2, 4, 6, 8, 1, 7

I found a chest with a unlocking puzzle that was pretty hard. It required 6 moves, each with 4 possibilities (3, if you discard the move that undoes the previous move), and as I couldn't figure it out, and wasn't really up for manually trying the 729 different combinations, I wrote a Ruby script for brute-forcing the problem. The script isn't very elegant, but it didn't take very long to write, and it was satisfying to see it solve the puzzle. :) The script is here, and the solution can be seen on the right.

By the way, an example of a more difficult puzzle using the same rules is this:  .- 12 -.         |   d  | 8 c.. 3         7  ..b 4 | a   | '- 65 -' which is unsolvable in anything less than 12 moves (2, 4, 6, 7, 8, 1, 5, 3, 2, 4, 5, 7).

Nobunaga
The first time I reached this guy, I didn't play very thouroughly, so I only had the following items to aid me: After having fought him a million times (and actually beat him once, only to be killed by the Golden Evil Statue), I decided that I could do better. I found an earlier savegame, and played through without using any health and grinding on some robots in the airship (that sounds a bit strange, actually :). So, this time I had a more reasonable inventory: and my Senpumaru was fully upgraded, which also should helped a bit. Anyways, it worked! I killed him in the second attempt :). The basic strategy for defeating Nobunaga was this: My strategy for Nobunaga was then:
 * Special M. Liquid (restores some magic)
 * Ekei's Keepsake (fully restores health and magic)
 * 4 Herbs
 * 4 Medicines
 * Secret Medicine
 * Magic Liquid
 * Special M. Liquid
 * Ekei's Keepsake
 * Evade lightning by alternately running to the front and the back of the room.
 * Evade tornado by either staying to the far back compared to Nobunaga, or to run in big circles around the room.
 * Evade lightning attacks by dodging.
 * Evade fire attacks by dodging.
 * Evade yellow earth attacks by staying directly below Nobunaga.
 * 1) Do all magic attacks with all weapons
 * 2) Pound his ass with Buraitou until you are low on energy
 * 3) Use Ekei's Keepsake
 * 4) Do all magic attacks with Buraitou, Hyoujin-Yari, and Dokoutsui
 * 5) Pound him with Buraitou until he starts flying (if he hasn't started already)
 * 6) Use all Senpumaru magic attacks
 * 7) Use Special M. Liquid
 * 8) Use remaining Senpumari magic attacks
 * 9) Pound him with Buraitou until he stops living :)

Golden Evil Statue

 * Block fireballs.
 * Beware of the spikes from the ground (they are marked, so you should just strafe to avoid them)
 * When it runs, you run (away from it!).
 * Evade flamethrower by running away.
 * Evade laser beams by running to the opposite side of the screen.
 * Evade flying heads by alternating running from side to side and shooting.