I was going to say ask some respected and all-knowing people to make a list of your favorite ideas so far and compare notes, but that might work as well ;P
It would be good, but how are we going to do that? Ask people of stupid ideas to delete their posts?
Concept: The Pure Utility Pokemon.
Description: A Pokemon based solely on team-playing. Reflect, Light Screen, Rapid Spin, Safeguard, etc.
Problems: Is the CAP project able to make something like this? To determine a balanced way in which this could work? Can we make a Utility Pokemon?
Concept: "Haze-ablaze"
Description: Doesn't necessarily have to do with fire, just wanted to have a memorable nickname for it. Basically, just a Pokémon that can use Haze with success. This can be done in any number of ways, for example: high speed, high defenses, or an ability that assists in this goal.
Concept: Anti-Ghost Rapid Spinner
Description: Should be neutral to most standard ghost attacks with balanced-good defenses. Scrappy isn't neccesarily required.
Flying-type counter:
A defensive pokemon that can take on the duel threats of Togekiss and Staraptor. Preferably resists Flying and cannot be weak to Flying (duh) or Fighting (due to Aura Sphere/Close Combat). Should have a consistent way to punish said Flying types, either by laying Stealth Rock or by having an Super Effective STAB attack.
Concept: True Garchomp Counter
Description: A Pokemon designed solely to counter Garchomp. It would be able to take Dragon, Ground and Fire moves well.
Concept: "Entry Hazards, what Entry Hazards?!"
Description: Slightly different from the previous Rapin Spinner ideas because with this as a concept we could deal with entry hazards through the typing (ideally poison, to suck up toxic spikes, and/or steel, to resist Stealth Rock), ability (Scrappy or an auto-Rapid Spin) and/or moves and stat layout. This concept gives more room for discussion and creativity than the standard Scrappy-spinner idea.
Concept: Gravity unit
Description: A Pokemon who can set up Gravity with little to no risk for itself, unlike Probpass and Jirachi, and preferably makes it usable by extending the amount of time it is in play. It may or may not have the moves to actually use Gravity - I cannot imagine it having enough moveslots left to sweep effectively, so the primary goal would be to make it viable to set up Gravity for something else.
Concept: Trick Room unit
Desciption: Same as above, except for Trick Room. This is less difficult to pull off, because for Trick Room to be not a danger for yourself you just have to be slow, whereas for a good Gravity you basically have to be a Bug or Grass type or something, or at least have very sufficient Defense.
Concept: Melee deterrent
Description: A Pokemon that can switch in with ease on the primary physical contact moves, most notably Close Combat, and try to trigger a trait such as Static to hamper them. I realize that for Heracross this is a double edged sword and for a slow Fighter such as Machamp or Hariyama it is a blessing, though, but it would be fun to pull off on Lucario. The problem is that one of the more dominant moves (Earthquake) is not a contact move, so eh.
Concept: Priority Specialist
Description: A Pokemon that attacks most effectively with high-priority moves. This Pokemon should learn nearly every +1 priority attack in the game (and maybe a +2???) and be able to do the most damage through those priority attacks, most likely via ability.
Concept: Stat Buster
Description: A Pokemon that can successfully take on popular Pokemon relying on stat boosting moves. May overlap with the "true Garchomp counter" idea.
Concept: The Pure Utility Pokemon.
Description: A Pokemon based solely on team-playing. Reflect, Light Screen, Rapid Spin, Safeguard, etc.
Concept: Armor Break
Description: A Pokemon designed to cut through opposing Pokemon's defensive stats.
Concept: Fast Tank
Description: It would be way cool to have a bulky tank fast for a change. Good defenses, nice speed but it could have average attack to make it balanced.
Concept: "Haze-ablaze"
Description: Doesn't necessarily have to do with fire, just wanted to have a memorable nickname for it. Basically, just a Pokémon that can use Haze with success. This can be done in any number of ways, for example: high speed, high defenses, or an ability that assists in this goal.
Concept: "Great Lead Poke"
Description: Inspired by Doug's post above this one. Basically, a lead that's able to disrupt the standard opening Pokemon, be it by threatening them or being able to nullify their standard strategy.
Concept: Defensive Cleric
Description: A supporter that can heal its allies and withstand many attacks. Something along the lines of Chimecho, but more defensive and possibly absorb status inducers.
Concept: A boon to weather teams
Concept: FEAR
Concept: The ultimate Baton Passer
Concept: Toxicroak/Stallrain of sand
Concept: Reversal of Worlds / Ribbon
Concept: Explosion Glass Cannon