- Highest tiered Prankster Pokemon
- Gets dual screens, Thunder Wave, and Taunt
- Good Attack allows it to hold its own if Taunted
- Can shut down other Pranksters, as a Dark type with Taunt
- Slow (doesn't really matter though)
- Somewhat frail
Grimmsnarl is really good as a screen setter. It has better HP than any other Prankster Pokemon, with or without screens, meaning it can be a valuable asset. Its Dark typing also allows it to block other Pranksters.
- Good lead, with Spikes, Thunder Wave, and Toxic
- Nice Defense, though the bad HP weighs it down
- Amazing defensive typing
- Not a very good attacker
Klefki is better in the lower tiers, where it can severely cripple Pokemon with its myriad of annoying moves. Its typing allows it to resist quite a few Pokemon, and it's also immune to Toxic.
- Brilliant Special Attack and Speed
- Varied movepool
- It's better as an offensive Defiant Pokemon, really only using Prankster for Thunder Wave, Nasty Plot, and maybe Defog/Agility
- A bit weak on the defensive side
Thundurus seems better as a Defiant attacker. It works as a Prankster, but it lacks the versatility that some of the other Prankster Pokemon have.
- Excellent Special attack and Speed
- Varied movepool
- Gets moves like Tailwind, Defog, Taunt, and Nasty Plot for Prankster
- Somewhat frail
Tornadus is pretty solid, even though it only gets a few moves worth using affected by Prankster. It can be support with Defog and Tailwind, or go offensively with Nasty Plot.
- Excellent Speed
- Wonderful moves like Fake Tears, Encore, Taunt, Protect, Substitute, Defog, Light Screen, Tailwind, and Toxic
Whimsicott is quite possibly the best Prankster Pokemon in Doubles, due to the gargantuan amount of beneficial moves it gets. If it's Taunted, it can also be a decent attacker with its Speed.
- Very fast
- Gets moves like Encore and Nasty Plot
- Can shut down other Pranksters thanks to the Dark typing
- Extremely frail
- Generally outclassed by Grimmsnarl
Liepard is in Untiered for a reason. It's too frail, and Grimmsnarl is far and away the better Dark type Prankster Pokemon. It gets screens and Thunder Wave, generally better than Encore and Nasty Plot on a Prankster Pokemon.
- Gets dual screens, Thunder Wave, Yawn, and Fake Tears
- Decently fast
- Average defenses and Special Attack
Meowstic is decent in PU, but it's just not very good in the higher tiers. Moves like Knock Off are common, and Meowstic is too frail to live more than one or two super effective hits.
- Gets moves like Toxic, Recover, Will-O-Wisp, Disable and Protect to be incredibly annoying
- Dark/Ghost typing gives it just one weakness
- That one weakness is very common in competitive, plus it doesn't resist many types
- Pathetically weak, both offensively and defensively
Sableye is a nice support Pokemon, but its garbage defense lends it to being destroyed by a lot of moves, including the omnipresent Fairy types. It was better with its Mega (even though it lost Prankster), but now that's gone, and Sableye is reduced to a ghost of its former glory.
In singles, the best Prankster Pokemon are probably Grimmsnarl, Klefki, and debatably Tornadus. In doubles, Whimsicott is the clear winner, with Grimmsnarl being very solid as well. Meowstic, Thundurus, and Tornadus are all decent in the lower tiers, but they usually aren't better than Klefki, Whimsicott, and Grimmsnarl. You have almost no reason to use Sableye and Liepard.
Hope I helped!