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: Pokémon Colosseum
Series as a Whole
Creepy Awesome: Cipher is pure evil and the patron saints of Paranoia Fuel for the cold, calculating efficiency with which they do their work, subverting as many protection fallacies as they think they can get away with. On the other hand, said cold, calculating efficiency and genre savviness has drawn them a number of fans.
Crowning Music of Awesome: Miror B. in both games has great battle music. The salsa-ish beat to go with his Ludicolo team in Colosseum is fitting and popular. And the funky disco of his XD theme can get stuck in your head for days. Having two such popular themes contributes to Miror B.'s status as an Ensemble Darkhorse.
There are quite a few epic battle themes in this game. The Cipher admin theme and Evice's theme stand out in particular.
Draco in Leather Pants: Venus and Lovrina are this in-universe, each having in-game fan clubs devoted to them.
Also, in real life, Dr. Ein form Colosseum and Ardos from XD have small fangirl followings.
Hell, pretty much every character in the entire first game is a darkhorse. Rui, Ein, Venus, Nascour and Dakim all have their followings; the only character who doesn't is Evice, mainly because he has very little to go by personality-wise.
Overly Long Gag - Watching Rayquaza faint. It takes forever to just fall over, giving the impression that Rayquaza is just a sore loser.
They Changed It, Now It Sucks: Fans were asking for a more plot-driven and Darker and Edgier take on the series since Gen I. Colosseum comes out and what's it criticised for? "It's not like Pokemon Ruby And Sapphire". They were not nice to Colosseum... however they lightened up around time for Mystery Dungeon and Ranger, and Colosseum gets a lot more love nowadays for its innovation.
Accidental Innuendo: A construction worker in the Pyrite Hotel says "Apparently some rich fellow ordered the colosseum built. I'm amazingly stiff."
There's also a glitch that allows you a chance of finding Shiny Pokemon. However, there was no guarantee they'd stay shiny after purification and trading to another game. Again, this was fixed in XD, where no Pokemon can be shiny.
Moral Event Horizon: Dr. Ein crosses this just by inventing the Shadow Pokemon system (without a shred of remorse, and actually with a desire to improve it), and Evice and Nascour just by leading the whole operation. Particularly Evice since he oversaw all these despicable actions while posing as the friendly mayor of Phenac City.
Narm: The tattoo Wes has, a horizontal white stripe over the bridge of his nose and cheeks, does not look intimidating at all.
Play the Game, Skip the Story: Fans and former fans demanded a more plot-driven Pokémon game or for a Darker and Edgier entry to the series. They get Colosseum and...the responses are either "WTF where are the wilds?" "Why is this not like Pokemon Red or Blue?", "Shadow Pokémon? WTF are they babbling on about I wanna EV train!", "Double Battles? I HATE Double Battles!", while the Darker and Edgier stuff was mostly completely ignored by the "Pokémon is kiddy" age-ghetto types.
Although some people actually did pay attention. This is like the Ensemble Darkhorse of games in the franchise, after all.
Scrappy Mechanic: Shadow Rush in Colosseum inflicted recoil damage, which the computer tended to use to deny a Snag by forcing a self KO (Which is really annoying with Colosseum's use of Save Points and leads to much back tracking). This is fixed in XD. Now there are more Shadow moves than Shadow Rush and only Shadow Half (reduces the HP of all Pokémon on the field by half) and Shadow End (deal great damage but reduces the user's HP by half) have recoil (both appear only on end-game snag targets), but they have the same lethality as False Swipe, which benefits the player.
Hyper Mode in all its lose a turn glory - especially if said Pokemon is low on health and likely to get K Od before being able to take the opponent down first.
Can be seen as a blessing if you're interested in purifying all pokemon quickly; the pokemon at a cost of a lost turn will also gain happiness points, reducing the amount of time needed to purify it.
That One Boss: Applicable to any and all bosses who own Legendary or third-stage/uber Pokémon. However, a rather early game, and verymaddening example, is Dakim, who uses a brutally effective strategy to utterly destroy you: One Pokémon Protects (making itself immune to damage), the other uses Earthquake. Next turn, the roles switch. So you either eat Earthquakes until they run out of PP for Protect, or use somthing like Encore to screw their strategy up. When you take into account that Dakim has Entei, and Entei is Fire-type, which takes supereffective damage from Ground-type attacks, which is whatEarthquakeis,well...
Uncanny Valley: The way Rui's eye bulge to the sides makes her face quite unsettling.
Moral Event Horizon: Cipher as a whole crosses it in the first scene (as if they weren't on the other side of the line already) with the destruction of the S.S. Libra, which is confirmed to kill several people.
Individually, we have Snattle's imprisonment of an entire town's population (apparently using violence no less), Lovrina's corruption of Shadow Lugia, and Ardos attempting to get Michael and everyone else within the area killed.
Paranoia Fuel: In XD, Cipher Peons have a tendency to drop down from the ceiling when you least expect it. There's also one time where you get on an elevator alone, and you come out of said elevator with a Peon behind you.
Greevil not only has access to the three Legendary Birds, but also Lugia, as well as three Pokemon that are fairly strong in their own right.
Snattle's 2nd fight is also fairly brutal on its own, mainly due to his Shadow Starmie being a decent sweeper and being fought a long way away from a healing machine on either end, but you fight the smartest grunt in the franchise right afterwards.
They Changed It, Now It Sucks: The things they didn't keep the same rubbed some fans the wrong way, particularly changing Orre into a much more habitable place, thus losing its "edge."