A parachuting Cartoon Creature that evolves into a multi-armed Poison/Ground spider. It is notable for being the first CAP with a specific goal in mind: its purpose was to be a pure team-support Pokémon.*
An Electric/Water shrimp meant to be a jack-of-all-trades/utility counter (but is limited in how much it can do at a time thanks to the series' four-move limit), but primarily used as a sweeper due to a loophole on its ability.
Gone Horribly Wrong: The aforementioned loophole, enabling it to spam fast, recoil-less-Life-Orb-boosted attacks from its bizarrely expansive movepool. It even had the raw bulk to be virtually unkillable - and it was the last straw before the CAP Pokémon received a massive nerfing.
A Fighting/Dark voodoo doll meant to be a perfect partner for Togekiss (but in practice has done better with Zapdos). Also the last CAP project to be created using Generation IV parameters.
Consolation World Record: Voodoom was made with the goal to "Pick a good-but-not-great OU Pokémon, and design the perfect teammate for it, similar to the way Celebi & Heatran, or Blissey & Skarmory complement each other so well on competitive teams.". They failed at making a teammate for Togekiss, but have succeeded (The staff claims it was the most successful CAP) at making one for Zapdos.
As the point was simply to find out the dynamics behind "perfect teammates," while not having the CAP turn into a Game Breaker like some of the other CAPs, yes, Voodoom WAS the best CAP. Players learned a number of things about perfect teammates, and Voodoom isn't a Game Breaker (except MAYBE with Zapdos.)
Elemental Absorption: Its once-flavor ability LightningRod became viable with the Gen. V change that it nullifies all Electric-type attacks.
Frankenstein's Monster: The justification for Voodoom's electricity-absorbing abilities is that to evolve, its demi-canon pre-evolution Voodoll has to get struck by lightning via a needle through the heart. Frankenstein was cited as inspiration for this.
Gone Horribly Wrong: Subverted - while he failed at partnering with Togekiss, he is exceptional with Zapdos. because of this he's been called the most successful CAP to date.
Hollywood Voodoo: In a sense, Voodoom subverts this and plays it straight. (primarily the latter.) Some people had the idea to allow Voodoom to both bless (Louisiana voodoo) AND curse (Hollywood voodoo) people with its pins, but it's still a gigantic voodoo doll (which only Hollywood and Louisiana voodoo use: other Voudoun branches do not use them.)
Voodoll plays the trope even straighter. It's basically a normal voodoo doll.
Improbable Weapon User: A needle. Well, not exactly improbable for him since he's a voodoo doll, but still not something you commonly see.
The first two CAPs of Gen V, as well as the first two be part of an (entirely canon) evolutionary line and, in Tomohawk's case, the first Flying-type CAP. Specifically, a Flying/Fighting tigergryphon that is meant to help the player regain momentum (the upper hand). Scratchet, the pre-evolution, is a Normal/Fighting cub with a fluffy body meant to resemble an egg.
A fuzzy caterpillar with copper wings that evolves into a silver-plated cocoon and then a six-winged golden moth. Aurumoth is a Bug/Psychic-type (the first Psychic-type CAP) that attempts to embody "risk vs. reward".
Historical In-Joke: Cupra being awarded to the best of athletes references the ancient Olympic Games, and the species name of the entire line (Copper Specie, Free Silver, and Gold Standard) refer to coinage and bimetallism.
Railroading: Significant leaders of the CAP project declared Aurumoth more the Topic Leader's personal project than following the community guidelines as the CAP mission has in the past, as evidenced by poll slate choices being unvaried and toward a specific goal, and having the resulting pokemon not following the concept at all (being extremely un-risky to play).
CAP 5: Malaconda
A Grass/Dark serpent of myth that gives flexibility to sun teams while opposing common OU threats, especially Latias and Latios.
Attack! Attack! Attack!: Malaconda's level-up movepool consists solely of alternating Normal, Grass, and Dark attacking moves—as befitting its malevolent nature.
The Corrupter: Its mere presence causes those around it to become more hostile and evil.
Decided By One Vote: Its design was decided by two votes, actually: Amongst 230 votes, the results were 116 to 114.
Mighty Glacier: Great HP and Attack, with absurd Special Defense on that. However, while its thin Defense is complemented by its HP, its Special Attack (which it does not need) and Speed leave a lot to be desired for.
Reptiles Are Abhorrent: While most pokemon are selfish at worst or under a malevolent trainer's control, Malaconda is by nature chaotic and, in fact, amplifies vices in those who meet it.
Smug Smiler: In its artwork, Malaconda sports a devilish grin. In its sprites, it has a subdued, but more haughty smile.
Unofficial CA Ps
Note: These CAPs are conceptual, and thus, will never be actually available to use on Pokemon Showdown!, the main simulator.
The first unofficial CAP, made by a moderator and several CAP members, it is a Ice/Fire fox intended as part of a hail team.
Adaptive Armor: Sort of, as Froxfire's fur inversely scales with temperature.
Expy: Of Syclant, as it is a Glass Cannon that works best in hail, has similar base stats and base stat total, and has a secondary typing that neutralizes one of the Ice-type's weaknesses while doubling its weakness to Rock-type moves.
Fantastic Foxes: It's both a flame-tailed arctic fox that can control the weather.
Glass Cannon: Like Syclant, it has around base 70 for its HP, Defense, and Sp. Defense, but it has around base 120 for its Attack, Sp. Attack, and Speed.
Power Of The Storm: It manipulates the weather rather chaotically in a Pokedex entry, though in-game, it can only produce hail so with its Dream Ability.
Slippery Slope: Commonly cited as the reason Froxfire will not be officialized in any way, as if this CAP was accepted and used in competitive play, that would set a precedent for other, less thought-out pokemon to do the same, spoiling the integrity and mission of CAP as a whole.
Glacier Waif: It's two feet long, looks rather awkward and lanky, and has 119/111/109 defenses.
Hollywood Chameleons: Double-subverted. It can only change the color of its bands and ridge, but it can change its typing.
Lethal Joke Character: Its existence is a joke, but that doesn't mean that it isn't a competitive pokemon. Its defenses, movepool, and flexible typing can theoretically have it fit on a variety of teams.
Meme Acknowledgment: While it isn't an official CAP, its very existence as well as its Black and X/Y Pokédex entries are jabs at the memes around it.