i've been experimenting over the past two months, and here's what i came up with:

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Timid
-Baton Pass
-Agility
-Double Team
-Thunderbolt
mismagius has a speed baton set here, as most of my team can already pack a powerful punch, and speed is the only thing i'm lacking. i also stuck in t-bolt for annoying water-types.
Looks pretty good, I guess. Can't think of an item. I suppose you could try a pinch berry like the Lansat berry or Petaya berry or something, but you'd only be able to pass that once and you don't want to encourage the idea of waiting until Mismagius is in the red to pass. Then you'd only get one use out of Mismagius, too. Eh.

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Serious
-Earthquake
-Psychic
-Crunch
-Dragon Pulse
lucario has perfect stats for a mixed sweeper set. he has four of the best moves in the game and can take out almost anything.
Don't use neutral natures for mixed sweepers. Sure, nothing is detracted from, but nothing is gained, either. Mixed Lucario needs to be fast in order to work, so you want max speed here; go with either Hasty or Naive. Lucario's defenses aren't great, but they're good enough that it should be able to take a hit from something it's not weak to. Besides, Steel is a great defensive type anyway. I'd go with Expert Belt for the item; increasing super-effective damage on a Pokémon that's fairly likely to hold a super-effective attack is good. Personally, though, I'd switch Psychic with Dark Pulse and Crunch with Close Combat (or Brick Break, I guess, if you're paranoid about the defense drop). That way Lucario gets a STAB Fighting attack and can better deal with things like Blissey.

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Modest
-Safeguard
-Ice Beam
-Surf
-Recover
milotic is my special sweeper. throw up safeguard and then i can go to work with special attacks.
Safeguard Milotic... hm. A little unorthodox, but it's an idea. Just be aware that other Bulky Waters can easily outstall this set. Toxic might be a better idea than Safeguard, as then you'd be able to poison something like Slowbro that would otherwise be difficult to beat. Then your only real problem is something like Empoleon, which you probably won't see much of anyway. Leftovers is always a good item for Milotic.

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Adamant
-Megahorn
-Earthquake
-Swords Dance
-Rock Slide
there is no pkmn tougher than heracross, and i gave him a basic physical sweeper set.
Swords Dance Heracross should be Jolly, not Adamant. It needs the speed, and the attack boost Swords Dance gives it kinda makes Adamant overkill. Close Combat over Megahorn; Fighting covers more types than Bug does, and more common ones at that. You just don't see too many Grass-types these days, do you?

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Relaxed
-Block
-Toxic
-Light Screen
-Reflect
while playing against bronzong a few times, i've come to recognize the greatness he possesses as a sponge. even without reflect and light screen, he can take a beating due to his high defense and special defense, even from fire types due to his heatproof ability. i then block and toxic, preventing the opponent from escaping and have them suffer until their health is sucked away by the poison. throw in the levitate ability, and his only main weakness is against fighting moves.
I'd go with Levitate, personally. You basically have two options with Bronzong: either halve the damage from one super-effective attack and take full damage from the other, or completely remove the damage from one super-effective attack and take full damage from the other. Add to that the fact that Earthquake is more or less the most common move--very rarely will you find a team that doesn't have at least ONE Pokémon with Earthquake--and Levitate is simply a great deal more helpful. Oh, and one offensive move, if you can decide on one, might be a good idea. Otherwise, if your Bronzong is your last Pokémon and you come up against, say, a Lucario with Blaze Kick, you're sunk.

Modest
-Haze
-Flamethrower
-Will-O-Wisp
-Shadow Ball
i needed a good hazer that could also have a mixture of special moves, and weezing has the moves i needed to make it happen.
Don't know much about Weezing, but it looks decent from where I'm standing.
i also need a few suggestions for items.
thanks!