Anticlimax Boss: Numemon. He's fought in a late-game region and has about 300 HP, the single lowest value of any boss and on par with the weakest enemies in the game. Seeing as how you can fight him right after you defeat Giromon, there's no way you can really lose. Chances are you'll take him out in one blow.
Awesome Music: The game's soundtrack is surprisingly memorable, with some pretty nice ambient songs along with some rocking battle tunes. See this page for some choice samples.
Turboing through the areas to unlock Seadramon as a recruit, which in turn allows you to unlock Kabuterimon and Kuwagamon to unlock the gym upgrades early on, which makes getting the Digimon you want as your partner far easier.
Delaying the completion of the Toy Town sidequest in order to keep using the Monzaemon suit to get a free Ultimate.
Complete Monster: Analogman is a hacker who arrived in the Digital World and attempted to conquer it. He enslaved multiple Digimon to make living weapons that serve him unwillingly, viewing them as things to use and abuse. After being defeated by Mameo, Analogman tries to blow up the child. Returning as a ghost in Digital Card Battle, he hijacks and kills VenomMyotismon's mind and uses his body as a suit in an attempt to enact vengeance on the protagonist for defeating him before. Analogman's final appearance is in -next 0rder-, where he possesses Tsuzuki Shoma and unleashes a worldwide virus that painfully turns Digimon into violent Machinedramon clones. The process can also be enhanced by torturing the victims. His ultimate goal is to erase the entire Digimon multiverse from existence, just to see what happens next.
Cult Classic: Critical reception was mixed and sales weren't strong, but the game is remembered fondly by those who have played it. The consensus on it nowadays is that it's an interesting game with a lot of cool design concepts, as well as some great art direction and music, but its poor conveyance of important mechanics and information to the player make it very obtuse. Your enjoyment of it is highly dependent on how willing you are to put up with its idiosyncracies and whether relying heavily on external guides bothers you.
Disappointing Last Level: Not so much in terms of gameplay or story, but some versions of the game get increasingly buggy as you progress towards the end of the game.
Fan Nickname: The protagonist is traditionally called Hiro in Western circles (to the point where it's often misreported as his Canon Name). Japanese players instead call him "Analog Boy".
First Installment Wins: Out of all the Digimon World games, this is the one that most people remember and the one considered to be the most unique and worth revisiting in the future, so much so that Digimon World Re:Digitize and Digimon World -next 0rder- are both heavily based on its gameplay systems and have multiple callbacks to it.
Fridge Brilliance: Factorial Town is one of very few locations without toilet. It's inhabitants are machines or living faeces.
Early game, High Speed and Attack makes Spit Fire lethal, especially against single bosses who only have moves with long charge times. While not necessarily a high damaging move, the low MP cost coupled with high speed allows you to stunlock many foes. Sonic Jab is an even better version; not only is it's MP cost even lower, its attacks are also far quicker than Spit Fire.
Poison Claw is basically Sonic Jab with the added effect of inflicting the poison status on opponents. Because of how easy it is to spam and the effect having a decent 40% chance of triggering, it's a question of when rather than if it manages to poison the opponent, and once it does they have to deal with both gradual damage and their movement speed being reduced to a crawl. It's particularly crippling to melee-only Digimon, as the movement speed penalty means they'll have a hard time getting close enough to attack, and even if they do, there's a decent chance you can Poison Claw them before they get a chance to hit you.
Ice Statue has near-instantaneous casting time, high damage, and has a chance of causing paralysis to boot. If anyone asks why Megadramon's so popular, that's likely a factor.
Megalo Spark is basically the air-elemental version of Ice Statue.
Full Power/Full Potential. It raises all your stats by large amounts. In fact, the reason the Superboss is so hard is because he starts the battle by spamming it! Megadramon can use it too.
Bug. A spell that throws three bugs at your enemy, and they climb on them and explode. Because they can explode in random intervals, one can explode, only for your opponent to get back up and get blown up by ANOTHER.
Those techniques are nothing compared to the Monzaemon suit in Toy Town. If you get a Numemon, you can interact with the suit to evolve Numemon into a Monzaemon instantly. You can now breeze through most of the game with ease with your brand-new Ultimate Digimon, who can also learn Megalo Spark.
In Freezeland, you can trade items with three different Moyjamon. One of them will trade you S.Def.disk items in exchange for a Med.recovery, which you can buy for 500 bits at the store after you've upgraded it a couple times. S.Def. Disks sell for 2000 bits. With a few Med. Recoveries to start out, it's possible to get an infinite amount of money over the game as long as you don't recruit the Mojyamon.
Patamon in Gear Savanna. He acts like a wild Digimon: walking around in a rather small area and once you bump into him, he immediately triggers a boss battle. He's not particularly strong, of course, being a Rookie, but he can be troublesome if you happened to visit the area when your Digimon was also a Rookie (or a "bad" Champion like Sukamon, Nanimon, and Numemon) and underleveled. Also, you'll have to defeat him three times in a row. Be careful when you're going to Trash Mountain to devolve your Sukamon.
Similarly, Gabumon in Misty Trees due to the fact that he's partially hidden behind a tree. He may surprise you as he immediately triggers a boss battle when you unknowingly bump into him while looking for items.
The glitch where your partner's name at the startup screen would end with many extra "mon"s, Mojyamon dancing on the water, cloning items via the shop in the Gear Savannah, making the doors vanish in Toy Town with the DG Dimension move. There are so many it has a guide.
For whatever reason, you can keep feeding Digitamamon's stat-boosting meals to your Digimon partner even after he isn't hungry anymore. If you have a lot of money to spare, you can exploit this glitch to easily max out your Digimon's stats.
Thanks to a programming oversight, a Tanemon that doesn't weigh 10-20g and whose highest stat is Offense cannot Digivolve. You can use this to your advantage to easily get the "train Baby/In-Training Digimon ten times" upgrades for the equipment in Green Gym.
In the original Japanese version of the game, pressing and holding the triangle button after the name entry screen but before the intro movie starts causes the menu to pop up as soon as the game begins. Checking the inventory reveals that it's full of valuable items, including multiple copies of the Dummied Out Digivolution items, and while the items usually disappear and the game proceeds as normal as soon as the menu is closed, it's possible to skip the introduction sequence and keep all the items by using an Auto Pilot to avoid triggering the event. This bug was fixed in the second revision of the Japanese release and subsequently every localized version, however.
Misblamed: Many of the glitches in the game are a result of the English localization team.
Scrappy Mechanic: The Digivolution system as a whole is frequently criticized for being very cryptic and giving the player little useful information as to how exactly it works, with a frequent anecdote from players being that they could only ever get a Numemon as a kid because they couldn't figure out how to get anything else. When the game was finally datamined properly many years later it became apparent just how complex the system really was, making it even more egregious how little information the game gives you. Even the people who like the game will usually admit a guide is basically mandatory to enjoy it.
Greymon. He's built like a truck with almost 5000 HP and high defense, and he hits like one too. He'd make a pretty standard late-game boss if it weren't for where he spawns: he ambushes you without any warning outside of Jijimon's house in File City, otherwise a safe zone, once you talk to Jijimon after hitting 15 prosperity points, which you can do very early on. As soon as you leave Jijimon's house, he forces a battle via cutscene. You cannot avoid this without using an autopilot, so if you don't have one, you have to either defeat him or get wiped. It's extremely likely the latter will happen if you didn't see him coming, and he's still fully capable of giving a good fight even if you did.
Birdramon. Like Greymon, she also jumps you in what is otherwise a fairly low level area and forces a battle. She isn't as tough as Greymon, but she comes with Prominence Beam, a very powerful attack, and will spam it constantly. Unsuspecting players will likely also get wiped out by her.
Garurumon is pretty strong thanks to his Ice Statue (as described above). To make it worse, he will ask you for a rematch where you are unable to give commands to your partner.
Piximon only appears randomly on the screen, along with two other bosses, and you must walk in and out until you finally see him. Since he's right next to the entrance of Tropical Jungle, anyone that sees him can just pass him off as another boss, especially if you're not familiar with the fact that Piximon is an Ultimate level Digimon (though, to his credit, he does warn you of this fact before granting you the option to back away). He also proves to be a Pintsized Powerhouse, having 5000 health, powerful stats, an attack that causes confusion, and Bug, a skill that can actually hit multiple times. It's no wonder this guy has caused many deaths for many players.
WaruMonzaemon can come down to a Luck-Based Mission thanks to having both a move that buffs its strength that stacks and a massively powerful move that's impossible to interrupt and can stun your Digimon. Beating him purely comes down to how much he ends up spamming both those moves in quick succession.
Recruiting Monochromon. You need to play his shop minigame and earn at least 3072 bits. The problem is that this is essentially a Luck-Based Mission as you simply cannot meet this requirement without overpricing as many items as you can get away with, but both the kind of Digimon customers you get and the items that they want are random. On top of that, raising the price has a chance of making Digimon leave without buying anything. If you get too many Weedmon (the worst kind of customers who will complain about everything, often even when you lower the price), and/or if you don't get enough customers wanting Medicine (the most expensive item), or if too many Digimon walk out on you, it can just become flat out impossible. The minigame also takes a while to complete, both in terms of real and in-game time, which makes it even more frustrating when you fail and have to try all over again.
Penguinmon's Curling Mini-game is a bit of a challenge, and can take a couple tries before you beat him. If you don't, prepare to have to fish, because the only way to rematch him is to give him some, even after he is recruited. To make matters worse, there's a medal you can earn that's focused on getting a perfect score (10-0) in the game, which is much harder to do. Have fun.
Recruiting any of the three "pint-sized powerhouse" Digimon (Piximon, Mamemon, and MetalMamemon). The only way to find them is going into specific screens over and over until they spawn (the chances to run into them in the select areas are around an abysmal 5%). And even if you happen to run into them by chance, they're all tough bosses in their own right, meaning if you aren't prepared with healing items and a strong Digimon you might have to come back and go through the arduous process of finding them all over again.
Tough Act to Follow: Not necessarily the game itself (depending on who you ask, and how they feel about the First Installment Wins associated with this one), but your Digimon. Due to the life cycle nature of your partner, you only have a limited time with each one until they die from old age. This can lead to frustration when you raise a particularly powerful Digimon, especially if it hits Ultimate level, and then it dies, leaving you to raise another one. Depending on what your partner Digivolves into, you may be cursing it for not being as good a fighter as your previous Digimon.
Ugly Cute: One usually would not use the word "cute" to describe Bakemon, a Bedsheet Ghost whose only facial features are a large pair of pitch-black eyes and a gaping maw with visible pointed teeth, but raise one as a partner, and its vocalisations will consist of a high-pitched stereotypical "Ooh" ghost wail, and the same kind of high-pitched chirping as the baby Digimon.
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