I came up with this myself and is awesome for late game annoyance, and it usually kills at least one Pokemon (and leaves several asleep)
Jumpluff @ Wide Lens
Ability: Infiltrator
252 Spe / 252 HP / 4 SpD
Jolly Nature
- Sleep Powder
- Substitute
- Strength Sap
- Leech Seed
You come in and put the opponent to sleep, then Substitute. Once you're safe behind your sub, Leech Seed them and Strength Sap if they're a physical attacker, then stall from there. And if they wake up and break the sub, put them back to sleep. Try to force switches so you can get more opponents to sleep. Things that outspeed you are annoying for this, so I would recommend having some form of speed control. And Taunt is this thing's kryptonite, so if you think Taunt is coming, get out of there so you can get a free switch in. Note that you are walled by Grass types.