this is what i was going to have as my 6 but if you have suggestions tell me.

Blaziken(i already chose him)
Shiftry or Ludicolo
Huntail or Kingdra
Flygon or Salamence
Claydol or Alakazam
Magneton or Manetric

One thing that I'm well known for is using type hybrids. Mostly for their advantages, but obviously the choice is up to you in the end.

With that being said, here are my suggestions for your options.

Blaziken (since you already have him)
Shiftry (obviously, depends on what game you have)
Kingdra
Flygon (depends on what you are using this Dragon-type for. Both are pretty good, Salamence has better stats but a more common weakness...)
Claydol
Magneton

Most of these are for types, and they are pretty balanced. If you do end up with Ludicolo (if you're a Sapphire player), then I would switch out the Water slot for something else, perhaps a Steel (like Aggron) or Ghost (like Sableye).

If you really want to use Manectric (consider that it's solely Electric), I guess you can go for it.

Now that I've discussed that, here are some other options that might be good.

Aggron
Sableye
Tropius (works great as an HM slave if you want it to...)
Whiscash
Zangoose
Absol (both have high ATK)
Lunatone/Solrock (again, depends on game...)

Hope this helps!

AEPMT