- Ability – Effect Spore
- Stats –Special Attack (252), HP (252), Defence (4)
- Nature – Quiet/Modest
- Item – Sitrus Berry
- Move set – Energy Ball (stab), Sludge Bomb (stab), Moonblast, Protect
Ah Vileplume, what could this cute innocent looking grass Pokemon do in Trick Room? Well, for starters it has 110 SpA so it's best not to look down. Also with its respectable defences, it tanks quite well against Electric, Water, Fighting and Grass type Pokemon, but not against common threats of Fire, Ice and Flying (or rather, just Talonflame alone). However, there is a good reason why Vileplume is not used a lot in Trick Rooms...
Strength
So not only it has great resistance against Electric, Water, Fighting and Grass types, it also serves an as immunity to powder moves (especially Rage Powder!), other supporting Grass-type moves like Leech Seed which (Mega) Venusaur would use occasionally, and Poison moves like Toxic.
Combined with its Defence and SpD, it can always recover itself with Giga Drain or Moonlight to handle many offensive Pokemon. What's more, Effect Spore ability comes in pretty handy at times when it gets hit by a physical move, back then I would always lure Mega Kangaskan to Fake Out it and works like a charm.
Weakness
Being Grass and Poison type, that also means it’s weak to 3 common move types, which are fire, ice and flying Talonflame in the current metagame, Psychic Pokemon do make an appearance too once in awhile; so it's best to have partners to provide cover on the type disadvantage, which could easily take up 2-3 slots in your team.
Another problem that Vileplume faces is its Poison power, it's just not as strong as other Poison type contenders such as Dragalge, Seviper, and even Ariados who does a lot of Poisonous damage to Fairy Pokemon which usually have high SpD. Not to mention, it only has so few attacking moves making it quite predictable.
Moveset
I prefer Energy Ball to Petal Dance because I don't like the idea of being locked into one move for 2-3 rounds and being vulnerable at the same time, but if you must then the item should be switched for Lum Berry to cure the confusion afterwards. Sludge Bomb is very straight forward as it is one of the main STAB moves for the corpse plant, and Protect is self explanatory. Also; thanks to ORAS it can now learn Moonblast which can catch many opponents off-guard that's in too, especially against Fighting and Dark-type Pokemon, but maybe not so much on Dragons as they tend to have Fire and Flying moves.
Because of its inability to OHKO a Fairy Pokemon, another option is to have Toxic + Venoshock combo. It may seem silly, but here are my two reasons why Venoshock and Toxic combo is a good alternative. First, Toxic can never miss if a Poison type Pokemon uses it regardless of accuracy or evasion. This is great especially on opponents who rely on Minimize and other evasion tricks. Second, Venoshock’s damage will double up to 130 power (original 65) if the opponent is poisoned; officially making it the most powerful Poison move in the SpA category. So with Toxic + Venoshock combo, it will deal much greater damage in long term. Not to mention, Toxic also badly poisons the opponent too. But then again, this makes it extremely weak against Steel and Poison type Pokemon. So yeah.
Closing thoughts
(image credit to endless whispers)
Personally from my experience, I think Vileplume suits better being a support staller instead of a Trick Room offensive Pokemon. A defensive build would be full EV on HP and Defence with Bold nature for maximized Effect Spore usage, then give Black Sludge item for consistent recovery, Giga Drain will perfectly fit and adds durability for long term battle along with Black Sludge + Protect combo. As for the last two move slots, it has tons of support moves to spare like Aromatheraphy to get rid of status effects, so as Moonlight for staying in the battle, or even Toxic, Leech Seed, Worry Seed and many others. It can be used for Sunny team too with its Chlorophyll ability, but once again, there are better Chlorophyll users out there.
Well, that's my take on Vileplume. So Vileplume, I choose you (for a mixed Doubles team)! Glhf!