I came up with this myself and is awesome for late game annoyance, and it usually kills at least one poke (and leaves several asleep)
Jumpluff - Infiltrator Ability
252 Spe, 252 Hp, 4 S.Def
You come in and put the opponent to sleep, then substitute. Once your safe behind your sub, leech seed them and strength sap if they're a physical poke, then stall from there. And if they wake up and break the sub, put em back to sleep. Try to force switches so you can get more pokes to sleep. Outspeeds are annoying for this, so I would recommend having a poke with sticky web too. And taunt is this things kryptonite, so if you think taunt is coming, get out of there so you can get a free switch in. It is walled out by grass types, but those aren't too common.