I like this proposal; I've often found myself swapping between two pokemon that cover different things as I ladder, which this proposal will end. In the meantime, I'd like to present a set I've been using for a while:
Aggron @ Aggronite
Ability: Sturdy
EVs: 252 HP / 252 SDef / 4 Def
Sassy Nature
IVs: 0 Spd
- Curse
- Iron Head
- Metal Burst
- Rest
This looks somewhat like the normal Metal Burst Aggron at first glance, but this set also functions as a boosting mono-attacker. This set beats most of the common pokemon in the meta (and many of the uncommon ones) quite handily, except for Mega Charizard Y (Air Slash + Fire Blast koes), Mega Charizard X (but only if it has Will-O-Wisp, which most do, unfortunately), and Mega Venusaur (only with Sleep Powder). The basic idea here is to Metal Burst against frailer, more powerful attackers, and to set up against bulkier threats. Now, against these frail attackers, most people will opt to use a weaker attack first in order to break Sturdy, and then attempt to finish you with a stronger attack. However, this will not work because of your Aggronite. The first turn out, you shouldn't be Mega Evolving in order to preserve Sturdy unless you're up against something that obviously won't be able to finish you in one hit (e.g. Porygon2, Mega Venuaur, etc.). This also maintains the illusion that you're just a normal Aggron trying to abuse Metal Burst. However, on the second turn, Mega Evolve in order to use Mega Aggron's superior bulk and typing to survive whatever attack they throw at you next. For example, Choice Specs Greninja 2hkoes normal Aggron with Dark Pulse, but Mega Aggron's added bulk lets it survive 2 Dark Pulses, even if the first one was taken as normal Aggron. Against bulkier Pokemon, Aggron can simply Curse up, using Rest as neccesary, and defeat nearly everything with a +6 Iron Head. Rest makes it a lot easier to win PP wars, as the two turns spent sleeping, you aren't using PP. Rest also ruins most strategies that rely on passive damage, like Leech Seed (haha fuck you Whimsicott) and burns. The EV spread maxes out special bulk, and makes Earth Power from Kyu-B only a 3hko, allowing you to beat it with Metal Burst/Iron Head. Investment in Attack or Defense isn't needed, because you don't usually need to attack until you're boosted, and at that point investing in Attack makes little sense, as you already attain all the koes you need. Investment in Defense isn't needed either, because Aggron already has a titanic Defense stat (it lives a +2 Mega Garchomp EQ with no investment), plus investing in Defense lowers the damage you deal with Metal Burst from physical attackers. For example, Mega Heracross deals barely enough damage for you to KO it with Metal Burst when it uses Close Combat with the given spread. However, with investment in Defense, you miss the KO with Metal Burst and then he outspeeds and 2hkoes you. The reason this isn't true for special attacks is that (Mega) Aggron's Special Defense is poor enough that it needs the investment in order to survive the attacks in the first place. Sassy nature and minimum speed try to insure you go last, which is crucial (Metal Burst fails if you go first). I've managed to get to #7 on the ladder using purely this set (screenshot
http://prntscr.com/3wwydp ), so I think it's been pretty successful. Get out there and give it a try!
Adding on, this is how the set fairs against some of the more common pokemon in the metagame, in no particular order:
Kyurem-B: Win. They 3hko with Earth Power while you 2hko with Iron Head/Metal Burst.(You should Mega Evolve the first turn here, as Teravolt overrides Sturdy.)
Dragonite: Win. Either they bring you down to Sturdy with EQ and you KO with Metal Burst, or they use a different move and you Mega Evolve and begin setting up.
Mega-Mawile: This one is a bit tricky, but you lose only if they have perfect prediction. If they attack without boosting with SD, you win with a combination of Metal Burst/Iron Head. If they begin boosting with SD, Spam Metal Burst while throwing in the occasional Curse, they win only if they have Fire Fang (which is kinda shitty) or if they attack while you Curse.
Greninja: Win. You survive Hydro Cannon due to Sturdy and 1hko back with Metal Burst, and Dark Pulse does not 2hko.
Aegislash: Win. Shadow Ball only 4hkoes as long as they don't get a SpD drop, while Metal Burst 3hkoes.
Jirachi: Win. Iron Head only deals like 9% to Mega Aggron, so you can boost up and Rest off the damage, unless you are very unlucky.
Togekiss: Win. Iron Head has a 75% chance to 1hko max HP Togekiss and it only 3hkoes with Fire Blast.
Swagger Lvl 1 Magnemite: You will win this most of the time due to confusion not doing very much, unless, again, you are very unlucky.
Whimsicott: This depends entirely on if they have Taunt, since you can't 1hko with Iron Head, and Taunt will prevent you from Resting. If they don't have Taunt, you win 100%.
Mega Venusaur: If they have Sleep Powder, you lose. Otherwise, you win due to Leech Seed+Giga Drain not doing enough to stop you from stalling out all of Giga Drain's PP with Rest.(I suppose you would lose to HP Fire or Earthquake, but I've yet to see either of those moves.)
Mega Charizard Y: You lose to Air Slash+Fire Blast unless you are insanely lucky and both roll ABSOLUTE minimum, in case you win.
Mega Charizard X: You lose most of the time, but if they don't have Will-O-Wisp, you can Curse alongside Dragon Dance and win as normal Aggron if they have Flare Blitz over EQ, or Curse as Mega Aggron while they Dragon Dance if they have EQ.