CeleTran



Pokemon needed: Celebi, Heatran

Overview
CeleTran is a very effective defensive combination. Together they resist all types except Rock. Also, the main type weaknesses of one of the Pokemon is usually a resistance of the other.

Weaknesses
Switching is needed for this combination to work efficiently, so having a Spinner on the team would be recommended to keep away damaging entry hazards.

Moves
A good move for Celebi would be Leech Seed. Leech Seed makes this combination harder to take down, and any Grass Pokemon switching in can usually be dealt with by Heatran. Being a defensive combination, Explosion is not recommended for Heatran in this combination for obvious reasons. If you plan to use a Scarfed Heatran for this combination, an idea is to fill Celebi with support moves for Heatran (such as Leech Seed or Thunder Wave).

Abilities
Due to Celebi's Natural Cure, switch to Celebi when you expect a status move, unless the move induces Burn or Poison. In which case, switch to Heatran for a Flash Fire bonus or to just block Toxic. Flash Fire is very useful to absorb those super effective Fire moves for Celebi.

Items
Obviously, Leftovers is recommended for Celebi. Both Choice Scarf or Leftovers are recommended for Heatran. Choice Scarf is usually the best option so that the set can beat things like Infernape, Lucario, non-Scarfed Jirachi and other non-Scarfed Heatrans.

Roles
Heatran is usually the less defensive Pokemon in this combination, due to its use of a sweeper. However, there is no need to change Heatrans EVs and Nature completely just for this, as a Scarfed Heatran works well for this combination. Celebi works very well to open a sweep for Heatran, taking down things like Swampert and Gyarados which would wall Heatran. If you plan to use Heatran as a staller, don't expect the combination to do too much direct damage. This means you'll need more entry hazards and/or Toxic/Phazing support.

Counters and Anti-Counters
A good counter for this combination would be Ludicolo, but as Ludicolo is nonexistent in OU, you're pretty safe. Porygon2 could defeat this set too, but only if it traces Flash Fire. Infernape and Salamence could also counter this set, but it would need some prediction. Heatran itself, when carrying Scarf, can take on Infernape and OHKO with Earth Power. It is hard to find a Pokemon that anti-counters all these Pokemon, but your best bet is a fast Starmie, who can also fill in the role of the Spinner. An opposing Heatran can completely destroy this set too, but it is very situational.