Shin Megami Tensei: Persona 4

Completion bonuses:
Successfully complete the game to unlock "New Game Plus" mode with a cleared saved game file. In this mode, Death sometimes hides inside treasure chests. You will know when this happens if you are prompted to open or ignore the chest. If you defeat Death after the chest is opened, you will get the ultimate weapons for the characters.
.

Successfully complete the game with the true ending. Start a game in New Game Plus mode. A new Fusion section will be available, allowing you to fuse Izanagi-no-Okami.

Bonus weapons:
Complete one of the following dungeons, then return to it. Complete the indicated task in that previously completed dungeon to unlock the corresponding bonus weapon.

Kanji's bonus weapon: Defeat the extra Boss in Steamy Bath House.

Kuma's bonus weapon: Defeat the extra Boss in Opera House.

Main Character's bonus weapon: Defeat the extra Boss in Void Quest.

Naoto's bonus weapon: Defeat the extra Boss in Bonus Lab.

Yousuke's bonus weapon: Hidden in the Boss' den in Mysterious Shopping Street.

Yukiko's bonus weapon: Defeat the extra Boss in Yukiko's Castle.

Hidden skills:
Complete the indicated task to unlock the corresponding skill.

God Judgment: Fuse a Persona during the fusion forecast "Skill Change". Its effects are 50% HP gone from enemies, Light.

Hell Judgment: Fuse a persona during the fusion forecast "Skill Change". Its effects are 50% HP gone from enemies, Dark.

Hint: The Reaper:
The Reaper drops the strongest equipment in the game. You can find him everywhere but more frequently in Magatsu Inaba. Go to Magatsu Inaba during your second play through and open the normal treasure chests found there.

Hint: Mail Order Show items:
After awhile you will hear two students talking on your way to school.They will say something about a mail order show that is on every Sunday. After hearing this, press X to view your television and select "Mail Order Show". The show only gives you the name of the items and not their stats. The following is a list of the weapon and item stats.
Gamgirl3.

Genji Ayu: Restores 20 HP to one ally; cannot be used as cooking ingredient.

Giant Candy: Restores 50 HP to one ally.

Herbal Pill: Restores 50 HP to one ally.

Humunculus: Restores 50 HP to one ally.

Jingi Fundoshi: DEF: 72, EVA: 23.

Longevity Pill: Restores 50 HP to one ally.

Myth-like Sword: ATK-140 HIT: 80.

Paladin Armor: DEF 166, EVA 19, Effect: Counter physical low odds.

Power Belt: Raises your STR by 2 points.

Prize Sticker: Send in three off them for a prize. You get one Prize Sticker per item purchase. You can find a mail box in the south section of the shopping area.

Purple Suit: DEF 116, EVA 23, Effect: Counter physical low odds.

Slimeing Food: Restores 50 HP to one ally.