http://www.smogon.com/dp/pokemon/magmortar
I recently made this lead a few days ago while looking for a competent, unique lead for my OU team. After testing it out on several opponents, it has worked out very nicely on everything it has supposed to, catching many leads like Jirachi, Aerodactyl, and Swampert off guard.
[Overview]
The main benefit of this Magmortar set in OU is surprise factor, and with a good movepool, decent bulk and a sky high Special attack stat, knowing what Magmortar is going to do in the lead spot is very tricky, especially for those who only play OU and who aren't familiar with it.
This lead will win out over quite a few common leads in the OU metagame. Even leads that Magmortar has trouble against, like Metagross and Hippowdon, can still be taken out with good prediction, as well as the surprise factor this set brings, especially if the opponent prioritizes getting up Stealth Rock over attacking.
[SET]
name: OU Attacking Lead
move 1: Overheat
move 2: Mach Punch
move 3: Thunderbolt
move 4: Hidden Power Grass
item: Expert Belt
ability: Flame Body
nature: Rash
Evs: 20 Atk / 52 Def / 252 SpA / 184 Spe
[SET COMMENTS]
<p>With Magmortar's huge special attack stat, priority move in Mach Punch, and access to powerful moves like Overheat and Thunderbolt, he can catch common OU leads off guard with the sheer damage his attacks can dish out. STAB Overheat coming off of a 383 special attack stat is no joke. It will OHKO lead Jirachi and will bring frail leads like Azelf down to its sash, while Azelf and Jirachi can never OHKO Magmortar with any of their attacks. With the given EV's, Magmortar can always survive lead Jolly Aerodactyl's Earthquake and hit it down to its sash with Thunderbolt. It can also survive a Fake-Out and Close Combat combo from the standard lead Infernape, and then 2HKO with a Thunderbolt and Mach Punch combo after the defense drops from Close Combat are factored in. Mach Punch is an often overlooked move in Magmortar's arsenal, and although it is very weak, it will catch the opponent off guard after a strong attack and net you kills on the threats mentioned above.
<p>Slow, bulky leads aren't completely safe from Magmortar either. Hidden Power Grass OHKO's the standard Swampert lead after factoring in the boost from Expert Belt. Standard lead Metagross, even with Occa Berry, has a chance to be OHKO'd by Magmortar's Overheat. Magmortar can also 2HKO lead Hippowdon with HP Grass, but taking on Hippowdon and Metagross can be quite risky if they choose to attack instead of setting up Stealth Rock, as Magmortar will be OHKO'd by Earthquake.
[Additional Comments]
<p>The EV's are pretty self explanatory. As stated earlier, 52 EV's in defense will allow Magmortar to survive attacks from leads such as Infernape and Aerodactyl. 184 speed EV's are more for late game purposes, as it will allow you to outspeed and OHKO bulky Gyarados before a Dragon Dance, as well as outspeed many bulky Celebi, Jarachi, Shaymin and Dragonite variants. Special attack should always be maxed for obvious reasons, and the rest of the EV's are dumped into attack to help Mach Punch hit a tiny bit harder late game against threats such as Weavile, or other fast foes that are at dangerously low health and need to be finished off.
[Team Options]
<p>There are a few leads Magmortar can do almost nothing against, such as Tyranitar and Gliscor, and thus it is advisable to have a backup pokemon to switch into to take the potential Earthquakes aimed at Magmortar. Skarmory and Gyarados work well with Magmortar, as they can switch in on predicted Earthquakes, but one must be wary of Stone Edge from Tyranitar when switching in Gyarados.
<p>Having Rapid Spin support will greatly improve Magmortar's usefulness later on in the match, as it is stripped of 25% of its health every time it switches in on Stealth Rock.
[Optional Changes]
<p>Fire Blast can be used over Overheat if you don't like the special attack drop, but then you lose the chance of OHKO'ing Occa Berry Metagross. Fire Blast is also slightly less accurate, and making sure Magmortar's attacks hit is crucial in the lead spot.
<p>Hidden Power Ice can be used over Grass to take out the rare Dragonite lead, as well as to nail Dragonite and Flygon on the switch later on in the game. Swampert leads are much more common though, and without HP Grass you can't really do anything to the standard Swampert.
<p>Shuca Berry is a viable option to survive Earthquakes from the likes of Hippowdon, Gliscor, Tyanitar and Metagross leads, but then you lose the power to definitively OHKO Swampert and potentially OHKO Metagross. If you use Hidden Power Ice instead of Grass, you can reliably take out Gliscor leads with Shuca Berry though.
[Counters]
<p>As previously mentioned, lead Tyranitar and Gliscor can take anything Magmortar has and OHKO it with Earthquake. Lead Empoleon can take a Thunderbolt and hit back with a super effective water attack to take out Magmortar. Heatran and Blissey wall this set outside of the lead spot, and Starmie will always outspeed and kill Magmortar with Surf or Hydro Pump.
<p>Machamp can take an Overheat and hit Magmortar with a Stone Edge, OHKOing it. Roserade is usually faster than Magmortar and can put it to sleep before it gets hit with an Overheat, but in the off chance that Sleep Powder misses, Magmortar will make quick work of lead Roserades with Overheat and Mach Punch.