Decided this was worth a set rather than an OO mention because good revenge killers that can check Arceus are always awesome.
http://www.smogon.com/bw/pokemon/heatran
[SET]
name: Choice Scarf
move 1: Overheat
move 2: Hidden Power Rock / Hidden Power Ice
move 3: Dragon Pulse
move 4: Flamethrower / Fire Blast / Earth Power
item: Choice Scarf
ability: Flash Fire
nature: Timid
evs: 4 Def / 252 SpA / 252 Spe
[SET COMMENTS]
<p>Heatran can act as a potent revenge killer with a Choice Scarf and sun support, capable of revenge killing Darkrai, Mewtwo, and weakened Arceus. Its Steel typing is a huge asset over Choice Scarf Reshiram, granting Heatran an invaluable resistance to ExtremeSpeed, immunity to Toxic, and a neutrality to Stealth Rock. Overheat is Heatran's STAB move of choice, OHKOing Darkrai and Mewtwo in sunlight and dealing a massive amount of damage to Arceus. Hidden Power Rock, alongside Heatran's typing and Flash Fire ability, allows Heatran to check Ho-Oh, who is otherwise a serious threat to sun teams. However, Hidden Power Ice is also an option for its ability to OHKO Rayquaza. Dragon Pulse hits Palkia, Giratina-O, and Giratina for moderate damage, the latter two being unable to do much in return. Flamethrower provides a reliable STAB move for late-game sweeping, whereas Fire Blast obtains notable 2HKOs in the sun where Flamethrower cannot; more specifically Bulk Up Dialga and Arceus. Earth Power is also usable since it deals with other Heatran easily, and is Heatran's strongest option against Dialga in the rain. Heatran is an excellent check for Dialga in general, as few carry Aura Sphere and fewer still carry Earth Power.</p>
[ADDITIONAL COMMENTS]
<p>The EV spread shouldn't need much explanation, but a Timid nature is necessary, as Heatran cannot outspeed Darkrai or Mewtwo without it. Groudon support is vital for this set's success, as the raw power of Heatran's sun-backed STAB Fire-type moves is one of this set's biggest appeals. Entry hazard support is also important for this set, as Arceus needs to be weakened a bit before Heatran can safely take it out in one shot. A layer of Spikes also guarantees that Overheat will nearly always OHKO 252 HP / 4 SpD Groudon, even after a turn of Leftovers recovery. Kyogre is this set's worst nightmare, so Pokemon that can handle it, notably Ferrothorn for its ability to supply entry hazards, are necessary. Other good examples of Pokemon that can manage Kyogre are Palkia, Zekrom, and Giratina-O, the last of whom has incredible typing synergy with Heatran and also checks Groudon. Heatran does have the option of running Explosion to deal a bit of damage to Kyogre, but this generally is not worth the moveslot given Explosion's relative weakness.</p>
And because I can (unless that's a faux pas or something let me know if it is):
QC Approved: 1/3
http://www.smogon.com/bw/pokemon/heatran
[SET]
name: Choice Scarf
move 1: Overheat
move 2: Hidden Power Rock / Hidden Power Ice
move 3: Dragon Pulse
move 4: Flamethrower / Fire Blast / Earth Power
item: Choice Scarf
ability: Flash Fire
nature: Timid
evs: 4 Def / 252 SpA / 252 Spe
[SET COMMENTS]
<p>Heatran can act as a potent revenge killer with a Choice Scarf and sun support, capable of revenge killing Darkrai, Mewtwo, and weakened Arceus. Its Steel typing is a huge asset over Choice Scarf Reshiram, granting Heatran an invaluable resistance to ExtremeSpeed, immunity to Toxic, and a neutrality to Stealth Rock. Overheat is Heatran's STAB move of choice, OHKOing Darkrai and Mewtwo in sunlight and dealing a massive amount of damage to Arceus. Hidden Power Rock, alongside Heatran's typing and Flash Fire ability, allows Heatran to check Ho-Oh, who is otherwise a serious threat to sun teams. However, Hidden Power Ice is also an option for its ability to OHKO Rayquaza. Dragon Pulse hits Palkia, Giratina-O, and Giratina for moderate damage, the latter two being unable to do much in return. Flamethrower provides a reliable STAB move for late-game sweeping, whereas Fire Blast obtains notable 2HKOs in the sun where Flamethrower cannot; more specifically Bulk Up Dialga and Arceus. Earth Power is also usable since it deals with other Heatran easily, and is Heatran's strongest option against Dialga in the rain. Heatran is an excellent check for Dialga in general, as few carry Aura Sphere and fewer still carry Earth Power.</p>
[ADDITIONAL COMMENTS]
<p>The EV spread shouldn't need much explanation, but a Timid nature is necessary, as Heatran cannot outspeed Darkrai or Mewtwo without it. Groudon support is vital for this set's success, as the raw power of Heatran's sun-backed STAB Fire-type moves is one of this set's biggest appeals. Entry hazard support is also important for this set, as Arceus needs to be weakened a bit before Heatran can safely take it out in one shot. A layer of Spikes also guarantees that Overheat will nearly always OHKO 252 HP / 4 SpD Groudon, even after a turn of Leftovers recovery. Kyogre is this set's worst nightmare, so Pokemon that can handle it, notably Ferrothorn for its ability to supply entry hazards, are necessary. Other good examples of Pokemon that can manage Kyogre are Palkia, Zekrom, and Giratina-O, the last of whom has incredible typing synergy with Heatran and also checks Groudon. Heatran does have the option of running Explosion to deal a bit of damage to Kyogre, but this generally is not worth the moveslot given Explosion's relative weakness.</p>
And because I can (unless that's a faux pas or something let me know if it is):
QC Approved: 1/3