Ninetales

Singles Sets
Ninetales @ Air Balloon
4 HP / 252 SpA / 252 Spe
nature: Timid
ability: Drought
- Fire Blast
- Energy Ball
- Hidden Power Fighting
- Flamethrower / Hypnosis

• Fire Blast is an incredibly powerful attack, making Ninetales very hard to switch in to. Energy Ball and Hidden Power Fighting can hit Politoed and Tyranitar very hard on the switch in, while Flamethrower is a more reliable alternative to Fire Blast. Hypnosis's low accuracy makes it hard to use, but a free sleep is very useful.
• If Ninetales doesn't predict correctly and another weather inducer comes in, then it will be left at a severe disadvantage. For this reason, Venusaur can make an excellent partner, as it is able to hit all other weather inducers for super effective damage and can switch in on them rather easily, while taking advantage of Chlorophyll when sun is up.
• A Pokemon such as Latios or Skarmory makes an excellent partner for Ninetales, able to switch in and threaten most of the Pokemon that threaten it.

Doubles/Triples Sets
Ninetales @ Focus Sash / Shuca Berry
4 HP / 252 SpA / 252 Spe
nature: Modest
- Heat Wave
- Energy Ball
- Hidden Power Fighting / Hidden Power Ice
- Protect

• Ninetales makes for a powerful weather starter, setting the stage for a sun team. Heat Wave takes advantage of the sun boost and is a spread move. Energy Ball hits Politoed, Rhyperior, and Water-types for super effective damage, while Hidden Power Fighting allows Ninetales to do some decent damage to Tyranitar. While Hidden Power Ice leaves you open to Tyranitar, it hits Garchomp and Salamence for super effective damage. However, since Hidden Power Ice maxes out at 96% on Garchomp, Ninetales requires priority or a faster teammate to complete the KO on Garchomp.
• Since Ninetales is the fastest of the weather starters, it requires adequate support to take on opposing weather. A Grass-type Chlorophyll abuser can take advantage of the weather and hit most other weather starters for super effective damage, while an Iron Ball lowers Ninetales's Speed to get sun up over rain, sand, or hail.
• Iron Ball allows Ninetales to underspeed and set up sun over every other weather starter except for Hippowdon, which allows Ninetales to work well on a Trick Room sun team. If using HP Ice, an IV spread of 31/31/31/31/31/2 should be used to maintain the lowest possible Speed.

Hidden Power Ice works great on the doubles set, hitting Garchomp and Salamence (and other Dragons as well, but mainly those two) for SE damage where the rest of your moves cannot. Interesting(ly terrible) to note is that Modest 252 SpA Hidden Power Ice maxes out at 95.65% on Garchomp, so Fake Out or other priority / faster-than-Chomp teammate is needed to ensure the KO.

Since you didn't list a nature for the Triples / Doubles set, I'll give my opinion:

I think Modest should be the main nature, as the only thing really threatening at Base 100 is Salamence (kinda? I guess if they carry EQ but Chomp usually takes that role), and you miss outspeeding neutral Garchomp. Modest gives it extra power and since there's not a whole lot it needs to outspeed (aside from Scarfers, I'll see what outspeeds Modest Tales later), Timid isn't really needed.

Now to switch subjects completely:

I think Iron Ball should get a mention, I've been running a Quiet 252 HP / 252 SpA / 4 Def @ Iron Ball set (Heat Wave / Energy Ball / HP Ice / Protect), and it works really well. (IV spread 31/31/31/31/31/2 to get HP Ice 70). It hits 47 (or 48 I don't remember) Speed with an Iron Ball, underspeeding all non-Iron Ball weather starters (aside from Hippo I think) so it's worked well for me on a TR Sun team, and I think it deserves a mention, if not a set of its own.

In Doubles, I've used Wide Lens with Heat Wave Ninetales to great success; it changes what is ordinarily an 81% chance of hitting both foes to a 98% chance of hitting both of them. Not necessary as a main item, but it's one of the best when other overused items are taken.

Modest is the best nature, and HP Ice is very useful. Iron Ball was added.