Ttar is usually fine even with max Attack IVs. And with its defenses, it can usually tank even its own hits for the first two Swaggers
Talonflame is also incredibly handy for taking out Klefki and Sableye especially. The former can't take Flare Blitzes, the latter can't inflict permanent status. Though my Whimsicott can usually take it if it's been paralyzed beforehand
Bisharp is also quite nasty if the opponent can use it well, though Klefki needn't fear it
Banded Scizors are evil with U-Turn. Noivern can take out one of my Pranksters, but usually get Paralyzed and is useless for the remainder of the battle
As before, anything stall oriented
Chansey takes anything below 400HP since subs and nonexistant attack
Volcarona is okay at stopping Klefki and Sableye, but Thundurus kinda murders it and it can only take one out. It's also the only thing I've ever seen a Lum berry on outside Ubers
As mentioned previously, Rotom-W is death
Mandibuzz wrecks things with Taunt and Knock Off. I can confuse it, but it tanks its own hits quite well. And as long as it gets a hit off withing the first three turns, it can usually down subs and either force a switch to Banette, or remove leftovers on whatever is out. I've been forced on multiple occasions to down Banette just to remove a pesky Mandibuzz
Porygon2 isn't around too much, but it has good defenses and oft carries Mirror Coat, allowing one with good skills to outplay my Pranksters
Scarf Ditto is annoying as ever. It can out Swagger my Pranksters and retreat immediately for something else (like Rotom-W >_>) To take advantage of my confusion/loss of momentum do to switching
Mega Mawile is annoying, esp. with TR support. Since then it outspeeds my Foul Plays. But its massive attack means in won't last many of its own hits. Azumarill is largely the same, but swapping TR for Aqua Jet
Jolteon and mega Manetric are both okay, but they have weak defenses, so Foul Play usually shreds them
Dusclops can't really heal, but as long as Sableye doesn't tag it with Will-O-Wisp, it can usually PP stall a lot of my Swaggers away
Speaking of PP stall, RestTalk Suicune shreds my Pranksters. They can do like nothing to it, and it can even remove the status I inflict on it with T-Wave/Will-O-Wisp, all the while forcing them to sacrifice precious Swaggers and Subs to keep it from KOing/Burning them with Scald. That's another one I have to leave to Banette
Contrary Serperior is the worst, thankfully T-Wave can usually keep it from being too much of a thing since it annihilates its Speed
And of course, Magic Bounce:
As always, Espeon can be annoying. Esp. if it swaps in when I'm Swaggering and not behind a Sub. It forces a switch, or me risking harming myself, while it can set up with Calm Minds or drop some screens. Though Foul Play does still do quite a bit of damage to its meager defense stat
Xatu has been used specifically to counter PrankSwag, so enough said. It even kills my Espeon (who I run to mess with people expecting all Pranksters
Absol sucks against Foul Play. Dies in one hit after a Swords Dance, and probs two without. Further, it can't do shit to Klefki without said Swords Dance. There's a reason I'm the only person that uses it >_<
So there's my nich counters. I think Own Tempo is also a thing? Avalugg usually has Sturdy tho. And Smeargle, while it has surprised me once or twice when I forgot about it (Own Tempo is that little of a thing), simply cannot take a couple Foul Plays, and if it's got Spore I can always just swap to Espeon and put it to sleep, thus removing it