Mischievous Heart is, in my opinion, one of the best abilities to come out of Gen. V and may come to be considered one of the best in the metagame, but who knows?
EDIT: It seems likely confirmed that the mechanics of Mischievous Heart increase the priority of all non-damaging moves (0 BP moves) by +1.
Here is a list of competitively relevant non-attacking moves that will be affected by this ability by their increased priority level (with help from Obi's Move Priority Guide):
And here are the Pokemon who can have this ability:
Erufuun
Erufuun is the fastest and arguably best abuser of this ability (and yes, Speed does matter, depending on what kind of priority these moves get and the obvious presence of other MH Pokemon in the metagame). Encore + Taunt, a combination shared only with the less-bulky Leperadusu, is a tremendous way to shut down ANY priority-less stat-uppers as well as Stallmons in just two moves. Leech Seed + Substitute + Taunt (+ Protect) is a deadly SubSeeding combo with priority. Grasswhistle is a fairly unreliable Sleep move; however it can be used in last-ditch efforts or in the lead position. Switcheroo can also be useful for Tricking Choice items, Flame Orbs, or what have you. Stun Spore, as well, has the advantage over Thunder Wave of having no immunities (except for the new Herbivore Pokemon, who don't seem very appealing at this point) while spreading paralysis.
Torunerosu
Not a strong contender for best MH Pokemon; however its powerful offensive stats could keep opponents on the defensive, where Taunt can come in handy. Other than that, it can't really do anything with the ability that other Pokemon can't do better.
Borutorosu
Borutorosu is a dangerous threat with Mischievous Heart. Access to Agility, Nasty Plot, and Substitute, coupled with its great offensive stats and MH may make it a necessity to plan for for all team-builders.
Sableye
Sableye is a fascinating MH Pokemon. It's the only one with Will-O-Wisp, which is mostly why it's featured here. Being able to cripple physical threats, especially Dragon Dancers, may prove to be very useful. Sableye can also set up Rain and Sun with priority and Psych Up (which won't really help it that much with those stats).
Volbeat
Volbeat has a dangerous set of moves with which to abuse Mischievous Heart. Encore, Tail Glow, and Baton Pass are all legal together, which is all Volbeat really needs to set itself apart as a dangerous team player. Tail Glow's +3 boost in BW is not something you want Volbeat to get away with priority-Passing.
Illumise
Illumise is just like Volbeat except with Growth instead of Tail Glow. Growth got a boost this generation, boosting Attack and Special Attack both, and Illumise can priority-Pass those boosts to a more threatening sweeper.
Leperadusu
Leparadusu stands apart with access to Nasty Plot, Thunder Wave, and Yawn, none of which make it particularly more useful than Erufuun, who is faster and bulkier. Being immune to Psychic moves may help, but its offensive stats and terrible defenses will probably keep it in Erufuun's shadow.
Overall, none of the Mischievous Heart Pokemon seem to be defensively talented; however, if they are able to switch in, they can be true menaces with their priority non-damaging moves.
Questions:
Could Mischievous Heart, if it does indeed give all non-damaging moves some sort of priority, change the strategy surrounding boosting stats and sweeping?
How will priority Substitutes, Thunder Waves, Encores, Taunts, etc. change the metagame, specifically how the different playstyles (offense/balanced/stall) strategize?
I think it'll be a huge metagame-shifter, personally. Anyway, discuss!
The ability could cause enormous ripples throughout the metagame and make otherwise UU-or-below Pokemon OU in their own right.Mischievous Heart: Non-attacking moves have a higher speed priority.
EDIT: It seems likely confirmed that the mechanics of Mischievous Heart increase the priority of all non-damaging moves (0 BP moves) by +1.
Here is a list of competitively relevant non-attacking moves that will be affected by this ability by their increased priority level (with help from Obi's Move Priority Guide):
+6: Helping Hand
+5: Magic Coat, Snatch
+4: Detect, Endure, Follow Me, Protect
+3: None
+2: None
+1: Stat up/down moves (Nasty Plot, Agility, Cotton Guard, Calm Mind, Fake Tears, etc.)
Support/Status moves (Aromatherapy, Baton Pass, Encore, Leech Seed, Taunt, Screens, Thunder Wave, etc.)
Recovery moves (Recover, Rest, etc.)
Weather moves
Field Effects: Gravity, Tailwind, etc.
Substitute
Sleep Talk (?)
Trick/Switcheroo
0: None
-1: None
-2: None
-3: None
-4: Counter, Mirror Coat (?)
-5: Roar/Whirlwind
-6: Trick Room, Wonder Room, Magic Room
Keep in mind, all priority attacks except for Extremespeed rest in the +1 priority bracket, meaning you can still Encore SD Scizor's SD instead of eating a powerful Bullet Punch. The same can be said for other Pokemon, like NP Infernape's Vacuum Wave or LeadApe's Fake Out, so Speed may still be crucial for nullifying threats who also carry priority.
+5: Magic Coat, Snatch
+4: Detect, Endure, Follow Me, Protect
+3: None
+2: None
+1: Stat up/down moves (Nasty Plot, Agility, Cotton Guard, Calm Mind, Fake Tears, etc.)
Support/Status moves (Aromatherapy, Baton Pass, Encore, Leech Seed, Taunt, Screens, Thunder Wave, etc.)
Recovery moves (Recover, Rest, etc.)
Weather moves
Field Effects: Gravity, Tailwind, etc.
Substitute
Sleep Talk (?)
Trick/Switcheroo
0: None
-1: None
-2: None
-3: None
-4: Counter, Mirror Coat (?)
-5: Roar/Whirlwind
-6: Trick Room, Wonder Room, Magic Room
Keep in mind, all priority attacks except for Extremespeed rest in the +1 priority bracket, meaning you can still Encore SD Scizor's SD instead of eating a powerful Bullet Punch. The same can be said for other Pokemon, like NP Infernape's Vacuum Wave or LeadApe's Fake Out, so Speed may still be crucial for nullifying threats who also carry priority.
Erufuun
Type: Grass
Other Abilit(ies): Slip Through
Stats: 60 / 67 / 85 / 77 / 75 / 116
Notable Moves:
Encore
Taunt
Leech Seed
Light Screen
Rest
Substitute
Grasswhistle
Switcheroo
Stun Spore
Charm
Endeavor
Other Abilit(ies): Slip Through
Stats: 60 / 67 / 85 / 77 / 75 / 116
Notable Moves:
Encore
Taunt
Leech Seed
Light Screen
Rest
Substitute
Grasswhistle
Switcheroo
Stun Spore
Charm
Endeavor
Torunerosu
Type: Flying
Other Abilit(ies): Competitive Spirit
Stats: 79 / 115 / 70 / 125 / 80 / 111
Notable Moves:
Agility
Rain Dance
Taunt
Torment
Rest
Substitute
Other Abilit(ies): Competitive Spirit
Stats: 79 / 115 / 70 / 125 / 80 / 111
Notable Moves:
Agility
Rain Dance
Taunt
Torment
Rest
Substitute
Borutorosu
Type: Electric/Flying
Other Abilit(ies): None
Stats: 79 / 115 / 70 / 125 / 80 / 111
Notable Moves:
Heal Block
Agility
Nasty Plot
Taunt
Rain Dance
Torment
Rest
Thunder Wave
Substitute
Other Abilit(ies): None
Stats: 79 / 115 / 70 / 125 / 80 / 111
Notable Moves:
Heal Block
Agility
Nasty Plot
Taunt
Rain Dance
Torment
Rest
Thunder Wave
Substitute
Sableye
Type: Dark/Ghost
Other Abilit(ies): Keen Eye/Stall
Stats: 50 / 75 / 75 / 65 / 65 / 50
Notable Moves:
Calm Mind
Sunny Day
Taunt
Rain Dance
Torment
Rest
Will-O-Wisp
Psych Up
Substitute
Recover
Nasty Plot
Trick
Other Abilit(ies): Keen Eye/Stall
Stats: 50 / 75 / 75 / 65 / 65 / 50
Notable Moves:
Calm Mind
Sunny Day
Taunt
Rain Dance
Torment
Rest
Will-O-Wisp
Psych Up
Substitute
Recover
Nasty Plot
Trick
Volbeat
Type: Bug
Other Abilit(ies): Illuminate, Swarm
Stats: 65 / 73 / 55 / 47 / 75 / 85
Notable Moves:
Moonlight
Tail Glow
Sunny Day
Light Screen
Rain Dance
Rest
Thunder Wave
Psych Up
Substitute
Baton Pass
Trick
Encore
Other Abilit(ies): Illuminate, Swarm
Stats: 65 / 73 / 55 / 47 / 75 / 85
Notable Moves:
Moonlight
Tail Glow
Sunny Day
Light Screen
Rain Dance
Rest
Thunder Wave
Psych Up
Substitute
Baton Pass
Trick
Encore
Illumise
Type: Bug
Other Abilit(ies): Oblivious/Tinted Lens
Stats: 65 / 47 / 55 / 73 / 75 / 85
Notable Moves:
Charm
Wish
Encore
Sunny Day
Light Screen
Rain Dance
Rest
Thunder Wave
Psych Up
Substitute
Baton Pass
Growth
Other Abilit(ies): Oblivious/Tinted Lens
Stats: 65 / 47 / 55 / 73 / 75 / 85
Notable Moves:
Charm
Wish
Encore
Sunny Day
Light Screen
Rain Dance
Rest
Thunder Wave
Psych Up
Substitute
Baton Pass
Growth
Leperadusu
Type: Dark
Other Abilit(ies): Limber/Unburden
Stats: 64 / 88 / 50 / 88 / 50 / 106
Notable Moves:
Torment
Taunt
Nasty Plot
Claw Sharpen
Sunny Day
Rain Dance
Rest
Thunder Wave
Psych Up
Substitute
Charm
Encore
Yawn
Other Abilit(ies): Limber/Unburden
Stats: 64 / 88 / 50 / 88 / 50 / 106
Notable Moves:
Torment
Taunt
Nasty Plot
Claw Sharpen
Sunny Day
Rain Dance
Rest
Thunder Wave
Psych Up
Substitute
Charm
Encore
Yawn
Overall, none of the Mischievous Heart Pokemon seem to be defensively talented; however, if they are able to switch in, they can be true menaces with their priority non-damaging moves.
Questions:
Could Mischievous Heart, if it does indeed give all non-damaging moves some sort of priority, change the strategy surrounding boosting stats and sweeping?
How will priority Substitutes, Thunder Waves, Encores, Taunts, etc. change the metagame, specifically how the different playstyles (offense/balanced/stall) strategize?
I think it'll be a huge metagame-shifter, personally. Anyway, discuss!