These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Digimon World 4
Game Breaker: Guns. They're very powerful, let you snipe at enemies from a distance, and if you have one with mods, you can equip Elemental Chips on them, turning them into Elemental Magic blasters that doesn't cost MP.
Also, while the digievolutions are generally way more powerful than the starters digimon, Susanoomon takes the crown. Not only he has the best stats of the game, his magics are also good.
That One Level: Dread Note in Venom Jungle. It's not uncommon for players to spend hours trying to get through this one.
That One Sidequest: Most of the sidequests in the game are really hard to accomplish. It's even more difficult when you're trying to get a digievolution, which generally requires the completion of the aftermentioned sidequests, but with more demands, such as exiting the dungeon with only 1 hp left.
And if you're up to get a Signature Weapon, you must beat every boss in Hard Mode in the right sequence WITHOUT TURNING THE CONSOLE OFF (You can still save the game, but if you ever turn the console off, you must restart the sequence). Just taking out all the bosses generally takes 5+ hours, and if at anytime a blackout occurs... well, bad luck!