This is my first go at UU. What really piqued my interested was when I read about the concept of a Moltres Toxic stall, so I built a team around it. I can really use some help with the EV spreads/natures in particular, because some of the analyses haven't been updated to optimize stuff like Speed for the UU metagame (Sceptile, for example). Thanks in advance.
Changes are in bold (Registeel was originally Claydol, and Blastoise was originally Slowbro):
Hariyama @ Leftovers
Ability: Thick Fat
EVs: 76 HP / 180 Atk / 252 Def
Impish nature (+Def, -SAtk)
~ Knock Off
~ Brick Break
~ Bullet Punch
~ Whirlwind
The lead. As for the Fighting move, I'm honestly not sure what to settle with because Hariyama's options are endless. Also, I am totally split between Bullet Punch and Ice Punch. Bullet Punch makes up for Hariyama's lackluster Speed and gives him more purpose as a lead, to surprise stuff like Ambipom. On the other hand, Ice Punch is stronger and boasts better type coverage. Hariyama's main goal is to Knock Off Leftovers and to create additional damage from Drapion's Toxic Spikes using Whirlwind, which later helps Moltres set up. As far as I can see, Hariyama and Drapion make a pretty impressive duo, even though they often accomplish the same things.
Drapion @ Leftovers
Ability: Battle Armor
EVs: 252 HP / 12 Atk / 244 SpD
Careful nature (+SDef, -SAtk)
~ Crunch
~ Toxic Spikes
~ Rest
~ Sleep Talk
Takes status, sets up Toxic Spikes so Moltres gets an additional slot, and adds some nice resistances/immunities. This team doesn't have trouble with Psychic-types on paper, but I always liked the concept of Pursuit. There are other options for Sleep Talkers, which would free up a slot for Pursuit, but again, this team doesn't really seem to need a trapper. Drapion mainly works in tandem with Hariyama.
Moltres @ Leftovers
Ability: Pressure
EVs: 248 HP / 148 Def / 112 Spe
Bold nature (+Def, -Atk)
~ Flamethrower
~ Roost
~ Substitute
~ Toxic
I really liked this concept when I saw it, though I'm not really sure what would be optimal for the last slot of this set. If Drapion and Hariyama can spread around Toxic Spikes and abuse Knock Off, respectively, then Toxic doesn't have as much use. However, banking on Drapion spreading Toxic Spikes that effectively doesn't seem smart, and I want Moltres to have an option against bulky Water-types, hence Toxic. It replaces Will-O-Wisp because Toxic is (a) more accurate, and (b) I don't want to be forced to switch out against Water-types after setting up a Sub.
Sceptile @ Expert Belt
Ability: Overgrow
EVs: 44 HP / 252 Atk / 212 Spe
Jolly nature (+Spe, -SAtk)
~ Swords Dance
~ Leaf Blade
~ Earthquake
~ Rock Slide
This team lacks speed, and I just really like Sceptile. It has very good type coverage with this set, hitting most everything. X-Scissor has been a consideration over Earthquake to handle Shaymin, but Moltres seems like a decent enough switch-in. I am thinking of switching this Sceptile to a SubSeeding variant in order to cause more switches and add to the Toxic Stall theme, but I have a feeling that would not give this team enough firepower. The Speed EVs are to outspeed Base 115s.
Registeel @ Leftovers
Ability: Clear Body
EVs: 252 HP / 6 Atk / 252 SpD
Careful nature (+SpD, -SAtk)
~ Stealth Rock
~ Curse
~ Earthquake
~ Ice Punch
Comes into a special attack from something like Yanmega and can either set up Stealth Rock or Curse, bolstering its already massive Defense while powering up its attacks, which boast excellent type coverage. Also, Curse ideally prevents things from just setting up on it. This team desperately needs the resistances a Steel-type provides, and a Special Wall for stuff like Yanmega, so Registeel seems like a good option.
Blastoise @ Leftovers
Ability: Torrent
EVs: 252 HP / 252 Def / 6 SpA
Bold nature (+Def, -Atk)
~ Surf
~ Rapid Spin
~ Toxic
~ Protect
Provides the obligatory Spin support for Moltres. Toxic hits stuff that avoids Toxic Spikes from Drapion, also making Moltres's job easier, while Protect stalls the opponent and scouts. Things like exploding on bulky Water-types, so hopefully I can catch that once in a while.
Basically, this team needs a Spinner, and Blastoise is my choice for now. I've considered Hitmontop over Hariyama as a lead so I could keep Slowbro (I really like the fact that Slowbro has Slack Off) over Blastoise, but that would require a lot of changes. Other things I'm conflicted about include the fourth moveslot for Moltres and where (else) I might want to stick Rest/Sleep Talk.
At a glance:






Changes are in bold (Registeel was originally Claydol, and Blastoise was originally Slowbro):

Hariyama @ Leftovers
Ability: Thick Fat
EVs: 76 HP / 180 Atk / 252 Def
Impish nature (+Def, -SAtk)
~ Knock Off
~ Brick Break
~ Bullet Punch
~ Whirlwind
The lead. As for the Fighting move, I'm honestly not sure what to settle with because Hariyama's options are endless. Also, I am totally split between Bullet Punch and Ice Punch. Bullet Punch makes up for Hariyama's lackluster Speed and gives him more purpose as a lead, to surprise stuff like Ambipom. On the other hand, Ice Punch is stronger and boasts better type coverage. Hariyama's main goal is to Knock Off Leftovers and to create additional damage from Drapion's Toxic Spikes using Whirlwind, which later helps Moltres set up. As far as I can see, Hariyama and Drapion make a pretty impressive duo, even though they often accomplish the same things.

Drapion @ Leftovers
Ability: Battle Armor
EVs: 252 HP / 12 Atk / 244 SpD
Careful nature (+SDef, -SAtk)
~ Crunch
~ Toxic Spikes
~ Rest
~ Sleep Talk
Takes status, sets up Toxic Spikes so Moltres gets an additional slot, and adds some nice resistances/immunities. This team doesn't have trouble with Psychic-types on paper, but I always liked the concept of Pursuit. There are other options for Sleep Talkers, which would free up a slot for Pursuit, but again, this team doesn't really seem to need a trapper. Drapion mainly works in tandem with Hariyama.

Moltres @ Leftovers
Ability: Pressure
EVs: 248 HP / 148 Def / 112 Spe
Bold nature (+Def, -Atk)
~ Flamethrower
~ Roost
~ Substitute
~ Toxic
I really liked this concept when I saw it, though I'm not really sure what would be optimal for the last slot of this set. If Drapion and Hariyama can spread around Toxic Spikes and abuse Knock Off, respectively, then Toxic doesn't have as much use. However, banking on Drapion spreading Toxic Spikes that effectively doesn't seem smart, and I want Moltres to have an option against bulky Water-types, hence Toxic. It replaces Will-O-Wisp because Toxic is (a) more accurate, and (b) I don't want to be forced to switch out against Water-types after setting up a Sub.

Sceptile @ Expert Belt
Ability: Overgrow
EVs: 44 HP / 252 Atk / 212 Spe
Jolly nature (+Spe, -SAtk)
~ Swords Dance
~ Leaf Blade
~ Earthquake
~ Rock Slide
This team lacks speed, and I just really like Sceptile. It has very good type coverage with this set, hitting most everything. X-Scissor has been a consideration over Earthquake to handle Shaymin, but Moltres seems like a decent enough switch-in. I am thinking of switching this Sceptile to a SubSeeding variant in order to cause more switches and add to the Toxic Stall theme, but I have a feeling that would not give this team enough firepower. The Speed EVs are to outspeed Base 115s.

Registeel @ Leftovers
Ability: Clear Body
EVs: 252 HP / 6 Atk / 252 SpD
Careful nature (+SpD, -SAtk)
~ Stealth Rock
~ Curse
~ Earthquake
~ Ice Punch
Comes into a special attack from something like Yanmega and can either set up Stealth Rock or Curse, bolstering its already massive Defense while powering up its attacks, which boast excellent type coverage. Also, Curse ideally prevents things from just setting up on it. This team desperately needs the resistances a Steel-type provides, and a Special Wall for stuff like Yanmega, so Registeel seems like a good option.

Blastoise @ Leftovers
Ability: Torrent
EVs: 252 HP / 252 Def / 6 SpA
Bold nature (+Def, -Atk)
~ Surf
~ Rapid Spin
~ Toxic
~ Protect
Provides the obligatory Spin support for Moltres. Toxic hits stuff that avoids Toxic Spikes from Drapion, also making Moltres's job easier, while Protect stalls the opponent and scouts. Things like exploding on bulky Water-types, so hopefully I can catch that once in a while.
Basically, this team needs a Spinner, and Blastoise is my choice for now. I've considered Hitmontop over Hariyama as a lead so I could keep Slowbro (I really like the fact that Slowbro has Slack Off) over Blastoise, but that would require a lot of changes. Other things I'm conflicted about include the fourth moveslot for Moltres and where (else) I might want to stick Rest/Sleep Talk.