I actually discovered (I beleive) the fastest way to make a poke pretty much OHKO most poke's in a double battle with a very simple tactic (i'm sure this is going to get spammed at some point).
Simply have a Medicham and Marowak in play. The the Wak will obviously be equipped with Thick Club, doubling it's attack and making it a threat right away. Now, if you can play your cards right, open with a different set of poke's and have it use Trick Room and give Medicham Lagging Tail, that way you can just start sweeping. So right now, you have a base 45 speed poke in Trick Room with a capped attack of 568. Already good right there. Make Medicham use Skill Swap. This will give Wak Pure Power as his ability, doubling his attack. This gives him a grand total of 1136 attack without increasing his attack through buff moves (you can do that if you want to breathe on an enemy to break every bone in it's body, since it's attack absolutely capped is 4546 Att. Recockulous. Btw, if you want to know just how strong that is, I calculated how much an EQ from this guy would do to a Shuckle with capped Def [614]. It would deal roughly 865 damage). He can OHKO a Skarm with Fire Punch. Anything with a ground type weakness with be absolutely slaughtered by Earthquake (you should have switch Medicham out immediately after this with a slow levitator like Bronzong). Any Water poke's posing a threat will be destroyed by Thunderpunch, or you could change your coverage and wipe out other types with Stone Edge (more powerful, less accurate, covers about the same shiz).
Yeah, I know. Really really strong attacker. Now, there are a few things you gotta watch for.
1) Wak does NOT have a good way to protect himself from Special moves, since his SpD is megear at best and if Trick Room isn't up he's prey to special sweepers.
2) Priority moves may wittle him down and he doesn't have a solid amount of HP.
3) It takes a little bit to set up, so you may try to use it, but you might get shut down before you do.
With this in mind, if you DO use this combo, make sure you got back up guys who can use Trick Room and such effectively.
Another little strat for you out there who want to use Baton Pass more effectively. Medicham can learn Bulk Up and Calm Mind. Now this wouldn't be too useful of information unless you knew you can also breed into Baton Pass. If you give him Recover as well, you might actually have a chance of maxing out Att, Def, SpA, and SpD before Baton Passing to something that doesn't need the speed boost from Baton Pass. However, a single poke with Haze, Roar, or Whirlwind will stop this in it's tracks and Medicham isn't the best defender. If you can manage to keep him alive long enough (you're gonna want your other poke using moves such as Reflect and Light Screen to help out), you can pass to make an oncoming poke God.