A very standard UU team from my experience. It has very good type coverage, at least on paper, and has managed to decimate a few OU teams.
Mesprit lead (Jolly)
@Choice Scarf
52 HP / 204 Atk / 252 Spe
Moves: [Zen Headbutt] [Trick] [Stealth Rock] [U-turn]
This is a somewhat standard scarfed lead. I like using it because people usually can not differentiate a scarfer from an offensive lead. In making them make a descision, I hold more control over the situation. If the opponent is a bulky lead, I will throw a trick their way then proceed to u turn out after they set up rocks or something similar. If i think they are going for the offensive, i just U-turn to a safer poke. No use in losing a wall-crippler early game.
Rock Polish Rypherior (Jolly)
@Life Orb
252 Atk / 4 Def / 252 Spe
Moves: [Earthquake] [Rock Polish] [Megahorn] [Stone Edge]
Considering all it takes is a single Rock Polish to set up a very dangerous sweep in the UU metagame with this beast, it earned a special spot in my heart. I have seen this pokemon sweep an entire OU team because of its amazing abilities and high attack. He has very solid type coverage as well. I have safe switches that cover his 3x weaknesses fairly well.
Sleep Talk Spiritomb (Bold)
@Leftovers/Lum Berry
252 HP / 116 Def / 140 SpD
Moves: [Sleep Talk] [Rest] [Will-o-Wisp] [Dark Pulse]
Having no weaknesses, I can usually get my opponent to send out his strongest pokemon to defeat this thing. That generally means that I can set up a will-o-wisp and stall, or I can predict and send in a direct counter to that poke. Aside from that, being a ghost, it can effectively work as a spin-blocker. This pokemon tends to outlive other stallers too, considering I am carrying sleep talk. One extra dark pulse before a switch can mean a lot as well.
Sub-Punching Poliwrath (Adamant)
252 HP / 252 Atk / 4 Def
@ Leftovers
Ability: Water Absorb
Moves: [Substitute] [Hypnosis] [Waterfall] [Focus Punch]
UUs form of Breloom for the most part. I enjoy sending this guy in on switches from Spritomb. I can almost always wall a hit to get off a Hypnosis then proceed to sub-punch. If i think they are going to switch, you can't go wrong with a STAB Waterfall. I do not carry Ice Punch because my Sceptile is running Dragon Pulse for any dragons I run across.
EDIT: Switched from Damp to Water absorb.
(Used to be Choice Arcanine)
Choice Scarf Moltres (Modest)
@ Choice Scarf
252 SpA / 4 SpD / 252 Spe
Moves: [Air Slash] [HP Ice] [Overheat] [Fire Blast]
Yet to try him out in conjunction with the team. Would be used to revenge kill problem pokemon or switch in on non-effective hits and force switches/land a KO. Will get some news about how it performs up ASAP.
White Herb Sceptile (Modest)
@White Herb
4 HP / 252 SpA / 252 Spe
Moves: [Leaf Storm] [Focus Blast] [Dragon Pulse] [Energy Ball]
Bear with me for a moment with this Sceptile. This thing is not meant to be a straight-up sweeper. He has very good speed and tends to outrun many other pokes even with a Modest nature. The beauty of this set is the pure power it can dish out twice in a row. The way this set usually works is something similar to Arcanine. I send it in as a "revenge killer." Most people will assume it is a Choice Specs setup and either switch accordingly, or sit in and get revenge killed as I lock myself into a move. If i use Focus Blast and revenge kill a Registeel, since it will hit a little harder due to my modest nature, that might lead them to believe that it is Specd' as well. (As you can tell, I love mind games.) Upon their switch, they would switch into something that resists fighting. I use leaf storm. They see the white herb pop up and send in a revenge killer. Either way, I took out a poke. Possibly two. Aside from that, even if they call my bluff, I can still pack a 140 base power STABed Leaf Storm. (Points for a working Sceptile that doesnt have to really sacrifice usability for raw power?)
I am very fond of my team. However, I need some input as to what i can do to fill obvious weaknesses. It is very weak to entry hazard teams, but I have no idea if Hitmontop would be a good replacement for Pilowrath.
I am also a bit new to the UU scene, so any other input would be greatly appreciated.

Mesprit lead (Jolly)
@Choice Scarf
52 HP / 204 Atk / 252 Spe
Moves: [Zen Headbutt] [Trick] [Stealth Rock] [U-turn]
This is a somewhat standard scarfed lead. I like using it because people usually can not differentiate a scarfer from an offensive lead. In making them make a descision, I hold more control over the situation. If the opponent is a bulky lead, I will throw a trick their way then proceed to u turn out after they set up rocks or something similar. If i think they are going for the offensive, i just U-turn to a safer poke. No use in losing a wall-crippler early game.

Rock Polish Rypherior (Jolly)
@Life Orb
252 Atk / 4 Def / 252 Spe
Moves: [Earthquake] [Rock Polish] [Megahorn] [Stone Edge]
Considering all it takes is a single Rock Polish to set up a very dangerous sweep in the UU metagame with this beast, it earned a special spot in my heart. I have seen this pokemon sweep an entire OU team because of its amazing abilities and high attack. He has very solid type coverage as well. I have safe switches that cover his 3x weaknesses fairly well.

Sleep Talk Spiritomb (Bold)
@Leftovers/Lum Berry
252 HP / 116 Def / 140 SpD
Moves: [Sleep Talk] [Rest] [Will-o-Wisp] [Dark Pulse]
Having no weaknesses, I can usually get my opponent to send out his strongest pokemon to defeat this thing. That generally means that I can set up a will-o-wisp and stall, or I can predict and send in a direct counter to that poke. Aside from that, being a ghost, it can effectively work as a spin-blocker. This pokemon tends to outlive other stallers too, considering I am carrying sleep talk. One extra dark pulse before a switch can mean a lot as well.

Sub-Punching Poliwrath (Adamant)
252 HP / 252 Atk / 4 Def
@ Leftovers
Ability: Water Absorb
Moves: [Substitute] [Hypnosis] [Waterfall] [Focus Punch]
UUs form of Breloom for the most part. I enjoy sending this guy in on switches from Spritomb. I can almost always wall a hit to get off a Hypnosis then proceed to sub-punch. If i think they are going to switch, you can't go wrong with a STAB Waterfall. I do not carry Ice Punch because my Sceptile is running Dragon Pulse for any dragons I run across.
EDIT: Switched from Damp to Water absorb.

Choice Scarf Moltres (Modest)
@ Choice Scarf
252 SpA / 4 SpD / 252 Spe
Moves: [Air Slash] [HP Ice] [Overheat] [Fire Blast]
Yet to try him out in conjunction with the team. Would be used to revenge kill problem pokemon or switch in on non-effective hits and force switches/land a KO. Will get some news about how it performs up ASAP.

White Herb Sceptile (Modest)
@White Herb
4 HP / 252 SpA / 252 Spe
Moves: [Leaf Storm] [Focus Blast] [Dragon Pulse] [Energy Ball]
Bear with me for a moment with this Sceptile. This thing is not meant to be a straight-up sweeper. He has very good speed and tends to outrun many other pokes even with a Modest nature. The beauty of this set is the pure power it can dish out twice in a row. The way this set usually works is something similar to Arcanine. I send it in as a "revenge killer." Most people will assume it is a Choice Specs setup and either switch accordingly, or sit in and get revenge killed as I lock myself into a move. If i use Focus Blast and revenge kill a Registeel, since it will hit a little harder due to my modest nature, that might lead them to believe that it is Specd' as well. (As you can tell, I love mind games.) Upon their switch, they would switch into something that resists fighting. I use leaf storm. They see the white herb pop up and send in a revenge killer. Either way, I took out a poke. Possibly two. Aside from that, even if they call my bluff, I can still pack a 140 base power STABed Leaf Storm. (Points for a working Sceptile that doesnt have to really sacrifice usability for raw power?)
I am very fond of my team. However, I need some input as to what i can do to fill obvious weaknesses. It is very weak to entry hazard teams, but I have no idea if Hitmontop would be a good replacement for Pilowrath.
I am also a bit new to the UU scene, so any other input would be greatly appreciated.