Nails
Double Threat
There are a huge number of great attacks in pokemon. Certain moves have shaped the metagame, forcing some pokemon into the bottom of the tiering barrell simply because of the threat of the move, while others are completely game breaking when unleashed and can allow one to sweep through an oppnent's team when used at the right time. The list is potentially huge, but I've done my best I think to narrow it down. If anyone has any problems with my list, please tell me!
Stealth Rock
This one move has undoubtedly shaped the metagame more than any other (however, the poll is based on which is the BEST move, not which has the greatest metagame impact). Certain pokemon who have the power to destroy the OU tier are barely used because of this move (think Yanmega). Rapid spinners are used solely to counter this move, and Ghosts are frequently used to counter the countering! Easily one of the best moves in Gen IV.
Substitute
A fantastic move, it can be absolutely gamebreaking when set up. While it doesn't deal damage by itself, it allows the pokemon to become far more effective at beating the opponent's team. It increases the viability of a number of moves, notably Focus Punch and Leech Seed, and is effectively used by a huge number of sweepers to ease prediction and block status. It is one of the most gamebreaking moves in pokemon when set up.
Spore
Argued by many people to be a broken move, spore easily makes the list of options. The ability to incapacitate an opponent and generate a free turn 100% of the time is a huge boost. Indeed, it could be argued that Breloom is viably simply because is has the move (nearly 98% use the move, and few pokemon have a move on their moveset more frequently). Definitely a game changing move when used correctly.
Taunt
Taunt is a great support move. It can block pokemon from setting up, and can be used almost singularily to dismantle stall. Again, it is a move that makes certain pokemon a lot more viable due to its inclusion in their movepool. Aerodactyl, while lacking bulk, makes for a great lead simply because it blocks the opponent from setting up Stealth Rock. Azelf is in the same situation, although to a lesser extent (due to having a large number of other useful moves). Taunt is the main reason that mew is the best baton passer in the game, as Ninjask can pass boosts a lot more easily, and yet is easily blocked.
Dragon Dance
A move that can be absolutely destructive when used correctly. It was arguably the main reason Salamence was banned (without it, mixmence would be a much smaller threat, due to the lack of the threat of dragon dance). When used once, your opponent generally has to sacrifice something in order to revenge kill. If used twice, you outspeed everything and can destroy the metagame. While admittedly most of the viable users would be threatening without the move, they are a whole lot more threatening with it.
U-Turn
While I tried to avoid putting damaging attacks on the list, U-Turn is an exception. It is in my opinion the best damaging attack in the game, as it is 100% used for creating momentum. It puts your opponent in an incredibly tough spot, as no matter what they do, you will have a counter brought in. The added damage is just a bonus.
Encore
A highly underrated move, and its usability is hurt due to a lack of good users. It produces a huge amount of free turns, because it forces so many switches. If your opponent tries to set up on you, they are forced to switch, as they risk being set up on themselves. A huge length of time also helps encore, 4-8 turns of incapacitation is something moves like spore wish they could have. Additionally, unlike status moves, it works through substitutes. When used properly, it can change games. It's also my personal choice for best move.
Honorable Mentions
Outrage
The one attacking move that I considered, it has shaped the OU metagame. It hits all types neutrally besides steel, which has largely contributed to the steel centralization. With 180 Base power counting STAB, and 100 accuracy, it is arguably the best attack in the generation.
Recover/Roost/Slack Off/Wish
This group of moves are fairly self explanatory. They allow pokemon to essentially live forever if you can't deal 54% or more in a single attack with leftovers factored in. While not at all gamebreaking, the moves nonetheless are incredibly useful.
Spikes
Similar to Stealth Rock, except potentially twice as powerful. However, not hitting flying foes and having very limited distribution hurts the move.
Earthquake
One of the most powerful moves in the game, it has great distribution and hits the best defensive type in the game super effectively.
Draco Meteor
Similar to outrage, Draco Meteor takes advantage of the fantastic coverage of Dragon type attacks and has absolutely huge power. Choice Specs Latias was broken largely because of this move. Fire Blast is a move with widespread distribution and is generally seen along side Draco Meteor because it hits the one type that resists it super effectively, leaving hardly anything safe to switch in.
Please vote and discuss!
Stealth Rock
This one move has undoubtedly shaped the metagame more than any other (however, the poll is based on which is the BEST move, not which has the greatest metagame impact). Certain pokemon who have the power to destroy the OU tier are barely used because of this move (think Yanmega). Rapid spinners are used solely to counter this move, and Ghosts are frequently used to counter the countering! Easily one of the best moves in Gen IV.
Substitute
A fantastic move, it can be absolutely gamebreaking when set up. While it doesn't deal damage by itself, it allows the pokemon to become far more effective at beating the opponent's team. It increases the viability of a number of moves, notably Focus Punch and Leech Seed, and is effectively used by a huge number of sweepers to ease prediction and block status. It is one of the most gamebreaking moves in pokemon when set up.
Spore
Argued by many people to be a broken move, spore easily makes the list of options. The ability to incapacitate an opponent and generate a free turn 100% of the time is a huge boost. Indeed, it could be argued that Breloom is viably simply because is has the move (nearly 98% use the move, and few pokemon have a move on their moveset more frequently). Definitely a game changing move when used correctly.
Taunt
Taunt is a great support move. It can block pokemon from setting up, and can be used almost singularily to dismantle stall. Again, it is a move that makes certain pokemon a lot more viable due to its inclusion in their movepool. Aerodactyl, while lacking bulk, makes for a great lead simply because it blocks the opponent from setting up Stealth Rock. Azelf is in the same situation, although to a lesser extent (due to having a large number of other useful moves). Taunt is the main reason that mew is the best baton passer in the game, as Ninjask can pass boosts a lot more easily, and yet is easily blocked.
Dragon Dance
A move that can be absolutely destructive when used correctly. It was arguably the main reason Salamence was banned (without it, mixmence would be a much smaller threat, due to the lack of the threat of dragon dance). When used once, your opponent generally has to sacrifice something in order to revenge kill. If used twice, you outspeed everything and can destroy the metagame. While admittedly most of the viable users would be threatening without the move, they are a whole lot more threatening with it.
U-Turn
While I tried to avoid putting damaging attacks on the list, U-Turn is an exception. It is in my opinion the best damaging attack in the game, as it is 100% used for creating momentum. It puts your opponent in an incredibly tough spot, as no matter what they do, you will have a counter brought in. The added damage is just a bonus.
Encore
A highly underrated move, and its usability is hurt due to a lack of good users. It produces a huge amount of free turns, because it forces so many switches. If your opponent tries to set up on you, they are forced to switch, as they risk being set up on themselves. A huge length of time also helps encore, 4-8 turns of incapacitation is something moves like spore wish they could have. Additionally, unlike status moves, it works through substitutes. When used properly, it can change games. It's also my personal choice for best move.
Honorable Mentions
Outrage
The one attacking move that I considered, it has shaped the OU metagame. It hits all types neutrally besides steel, which has largely contributed to the steel centralization. With 180 Base power counting STAB, and 100 accuracy, it is arguably the best attack in the generation.
Recover/Roost/Slack Off/Wish
This group of moves are fairly self explanatory. They allow pokemon to essentially live forever if you can't deal 54% or more in a single attack with leftovers factored in. While not at all gamebreaking, the moves nonetheless are incredibly useful.
Spikes
Similar to Stealth Rock, except potentially twice as powerful. However, not hitting flying foes and having very limited distribution hurts the move.
Earthquake
One of the most powerful moves in the game, it has great distribution and hits the best defensive type in the game super effectively.
Draco Meteor
Similar to outrage, Draco Meteor takes advantage of the fantastic coverage of Dragon type attacks and has absolutely huge power. Choice Specs Latias was broken largely because of this move. Fire Blast is a move with widespread distribution and is generally seen along side Draco Meteor because it hits the one type that resists it super effectively, leaving hardly anything safe to switch in.
Please vote and discuss!