If any of you need help on the bonus dungeon or the bosses, I'll try to help to the best of my ability.

Edit: Corncracker, what was Heartless Angel/Fallen One translated as?

New content, don't read if you don't want to be spoiled

Here's the new weapons info, from Gamefaqs:


Oborozuki
Strength: +7
Speed: +7
Stamina: +0
Magic: +0
Attack: +225
Defense: +0
Evasion: +50
Magic Defense: +0
Magic Evasion: +10
Runic, 2-Hand OK

Zwill Crossblade
Strength: +3
Speed: +7
Stamina: +3
Magic: +0
Attack: +220
Defense: +0
Evasion: +30
Magic Defense: +0
Magic Evasion: +20
Runic, 2-Hand OK
Special effect: Randomly casts "Sleep".

---

Apocalypse
Strength: +7
Speed: +0
Stamina: +0
Magic: +7
Attack: +250
Defense: +0
Evasion: +20
Magic Defense: +0
Magic Evasion: + 20
Bushido, Runic, 2-Hand OK
Special effect: Consumes MP to perform critical hits.

Save the Queen
Strength: +0
Speed: +4
Stamina: +3
Magic: +7
Attack: +240
Defense: +0
Evasion: +40
Magic Defense: +0
Magic Evasion: +40
Bushido, Runic, 2-Hand OK

---

Longinus
Strength: +7
Speed: +3
Stamina: +3
Magic: +0
Attack: +235
Defense: +0
Evasion: +0
Magic Defense: +0
Magic Evasion: +0
Runic, 2-Hand OK

Gungnir
Strength: +0
Speed: +0
Stamina: +7
Magic: +7
Attack: +240
Defense: +0
Evasion: +0
Magic Defense: +0
Magic Evasion: +0
Runic, 2-Hand OK

---

Zanmato
Strength: +7
Speed: +0
Stamina: +7
Magic: +0
Attack: +245
Defense: +0
Evasion: +30
Magic Defense: +0
Magic Evasion: +0
Bushido, Runic, 2-Hand OK
Special effect: Randomly casts "Holy".

Godhand
Strength: +7
Speed: +3
Stamina: +7
Magic: +0
Attack: +220
Defense: +0
Evasion: +0
Magic Defense: +0
Magic Evasion: +0
Special effect: Randomly casts "Holy".

---

Stardust Rod
Strength: +0
Speed: +0
Stamina: +4
Magic: +7
Attack: +180
Defense: +0
Evasion: +0
Magic Defense: +0
Magic Evasion: +0
2-Hand OK
Special effect: Randomly casts "Meteor".

Angel Brush
Strength: +0
Speed: +7
Stamina: +0
Magic: +7
Attack: +170
Defense: +0
Evasion: +0
Magic Defense: +0
Magic Evasion: +0
2-Hand OK
Special effect: Randomly casts "Confuse".

---

Scorpion Tail
Strength: +4
Speed: +4
Stamina: +4
Magic: +4
Attack: +225
Defense: +0
Evasion: +0
Magic Defense: +0
Magic Evasion: +0
Special effect: Randomly casts "Bio".

Final Trump
Strength: +3
Speed: +4
Stamina: +4
Magic: +0
Attack: +215
Defense: +0
Evasion: +0
Magic Defense: +0
Magic Evasion: +0
Special effect: Consumes MP to perform critical hits.

---

Dueling Mask
Strength: +6
Speed: +6
Stamina: +6
Magic: +6
Attack: +0
Defense: +40
Evasion: +10
Magic Defense: +40
Magic Evasion: +10
Special effect: +25% HP.

Bone Wrist
Strength: +5
Speed: +5
Stamina: +5
Magic: +5
Attack: +0
Defense: +10
Evasion: +10
Magic Defense: +10
Magic Evasion: +10
Special effect: +50% Strength, +25% HP, +25% physical damage.

Apocalypse: 150 Accuracy
Zwill Crossblade: 180 Accuracy, attacks with Wind Element
Zanmato: 150 Accuracy, attacks with Holy Element, does not randomly cast Holy
Oborozuki: 180 Accuracy
Longinus: 150 Accuracy
Godhand: 150 Accuracy, attacks with Holy Element, does not randomly cast Holy, cannot be Thrown
Save the Queen: 150 Accuracy
Stardust Rod: 135 Accuracy
Angel Brush: 135 Accuracy, cannot be Thrown
Final Trump: 230 Accuracy, same damage from Back Row
Gungnir: 150 Accuracy
Dueling Mask: As noted by crazylegsryan, it resists all Elements
Scorpion Tail: 150 Accuracy, same damage from Back Row, 2-Hand OK, attacks with Poison Element, cannot be Thrown
Bone Wrist: +50% HP, +25% Magic Damage, Perfect Hit Rate, incompatible with Merit Award

Coliseum:

Oborozuki -> Zwill Crossblade Vs Outsider
Zwill Crossblade -> Oborozuki vs Tonberry

Apocalypse -> Save the Queen vs Fiend Dragon
Save the Queen -> Apocalypse vs Brachiosaur

Longinus -> Gungnir vs Prometheus
Gungnir -> Longinus vs Muud Suud

Zanmato -> Godhand vs Yojimbo (instadeaths)
Godhand -> Zanmato vs Great Behemoth

Stardust Rod -> Angel Brush vs Dark Force
Angel Brush -> Stardust Rod vs Gamma

Scorpion Tail -> Final Trump vs Vector Chimera
Final Trump -> Scorpion Tail vs Ahriman

Dueling Mask -> Bone Wrist vs Daedalus
Bone Wrist -> Dueling Mask vs Duel Armor


Here's all the videos of the bonus bosses, and explanation of how to defeat them should be in the video description:

Upgraded dragons:

http://www.youtube.com/watch?v=Z1wUYGTWL0A Upgraded Ice Dragon

http://www.youtube.com/watch?v=p0ZJzJbXg_4 Upgraded Storm Dragon

http://www.youtube.com/watch?v=wRewQBa395M Upgraded Blue Dragon

http://www.youtube.com/watch?v=oChIsY8nNCQ Upgraded Earth Dragon

http://www.youtube.com/watch?v=4-lM7jumagQ Upgraded Skull Dragon

http://www.youtube.com/watch?v=ez4o_dc9nEA Upgraded Holy Dragon

http://www.youtube.com/watch?v=yTT2HM5mydo Upgraded Red Dragon

http://www.youtube.com/watch?v=emPN8qC128U Upgraded Yellow Dragon

http://www.youtube.com/watch?v=lbkwQHANbeA Kaiser Dragon (1)

http://www.youtube.com/watch?v=-R-v1qjX4to Kaiser Dragon (2)

Monster Pit bosses:

http://www.youtube.com/watch?v=eMczq11AxZM Earth Eater

http://www.youtube.com/watch?v=fPL4EG-8xv8 Worst Malboros

http://www.youtube.com/watch?v=hvSx3_xOdOw Dark Behemoth

http://www.youtube.com/watch?v=t3Wg3exuNZ4 Gargantua

http://www.youtube.com/watch?v=nNRti59YCp0 Abyss Worm

No Omega Weapon video, but he isn't much tougher than Kaiser Dragon, if not having more HP.