Oh my goodness,
thank you. I've been wanting this thread to happen so long, in fact I was thinking of posting one until this popped up!
This is the current team I'm building on for Super Singles:
Carracosta @ Shell Bell
Ability: Sturdy
Hasty Nature (+Spe, -Def)
252 Attack / 252 Speed / 4 HP
Shell Smash
Rock Slide
Aqua Jet
Waterfall
Venusaur @ Venusaurite
Ability: Overgrow -> Thick Fat
Bold (+Def, -Atk)
252 HP / 252 Def / 4 SpA
Leech Seed
Giga Drain
Toxic
Protect
Heat Rotom @ Choice Scarf
Ability: Levitate
Modest (+SpA, -Atk)
252 Spe / 252 SpA / 4 SpD
Trick
Volt Switch
Overheat
Shadow Ball
The Battle Maison, as many people say, can be really hectic due to the AI. Many of the opponents carry Quick Claw, and many low accuracy moves such as Blizzard and Thunder can not only hit, but it can also land a critical hit AND a status condition easily. If that wasn't bad enough, the upper levels are crawling with Quick Claw + OHKO Move, hence the reason why I chose a Carracosta with Sturdy as a sweeper. The reason why Carracosta carries Rock Slide instead of Stone Edge is to be on the safe side in terms of accuracy due to the unpredictable nature of the Battle Maison, and Carracosta also carries a Shell Bell to set up more Shell Smashes if its HP is full. Venusaur is mainly there to stall my opponents and check Carracosta's main weaknesses: Electric and Grass.
I'm looking forward to hearing tips and strategies from you guys, so far I've noticed that the best teams consist of only one sweeper, since having more than one can make your team very fragile.