Okay, lets get the perversity set out the way, then do the real unexpected set. (everyone is gonna do the Contrary set, leading to a quick counter to it.)
Leaf Storm-yeah yeah...
Hidden power[Rock]-covers 4 weaknesses with one move
Toxic-does more steady damage.
Mean look-Traps the foe, preventing super effective switch ins.
Leaf blade-grass stab, critical hits...
Swords dance-powers up attacking moves.
Iron tail-all power. Covers ice weakness.
Reflect/Light screen-more defensive power
Aerial ace-Covers Bug weakness
Leaf storm/energy ball-although he doesn't have perversity with this set, it's still damaging. Or just stick with energy ball.
calm mind-He powers up to be a threat with this.
hidden power [Rock]-covers most weaknesses with this.
reflect/Light screen-Gives added defense.
My personal favorite set (with Contrary)
Leaf storm-comes off with boosted power
hidden power [Rock]
Reflect-leads to the next move...
Mirror coat-Since your opponent will be more inclined to use special attacks due to reflect, this would work perfectly. It's pretty unexpected too.