I've recently tried out a niche anti-meta set:
Heatran (F) @ Leftovers / Balloon
Trait: Flash Fire
EVs: 252 HP / 252 SAtk / 4 SDef
Modest Nature (+SAtk, -Atk)
- Sunny Day
- Hidden Power [Fighting] / Will-O-Wisp
- Dragon Pulse
- Fire Blast
FBlast and Dragon Pulse provide good average as mentioned. HP Fighting is for none other than Tyranitar. Sunny Day is a counter to rain and perhaps sand (I find that sun is the easiest to deal with in general).
The key to using this set is to force your opponent out. In rain, enter against Nattorei or one of the steel types rain teams usually carry and use Sunny Day on the switch. Usually, if the opponent doesn't see a weather inducer on your team, they will be less careful with Politoed. Moreover, even if it's alive and comes in on the turn you use SD, the sun will still be up (since you attack after rain activates). Thus, you'll force your opponent at the least to take a sun-boosted fire attack as they try to reswitch and bring Politoed out again. If you are a risk taker, you can actually SD again on the turn you think Toed will come back in. Sunny day is also useful against balanced teams since most will either send a water type or somebody that knows EQ. If you have balloon intact, you can SD on the switch and then get off at least a sun-boosted FBlast before being forced out.
HP Fighting is specifically for T-tar since I find him to be too common these days. Due to the Special Defense boost, non-specs Earth Power is a 3HKO on the T-tars I've seen. A lot of people must know this since I've had so many T-tar switch-ins. HP Fighting will be a 2HKO, but you have to hit on the switch-in or else most likely Heatran will die (to EQ or Superpower usually). WoW is another option to cripple T-tar and requires less prediction. In this case, I would switch Dragon Pulse with HP Ice. If you really feel like it, you could use Sunny Day to lure T-tar in sand teams, but it's very hard to do practically since the first switch usually is a hard counter.
This set has done well the last twenty or so games I played, but I'll keep on testing and you guys another update.