First Attempt at a Team Build.

This is really my first attempt at a team build, I tried to make the team revolve a lot around Rain Dance and the effects that Rain Dance has on moves. So I may as well start it off.

CurlyEars/Audino
Sassy +Sp. Def -Speed
Regenerator
Leftovers
+148 HP +180 Def +180 Sp. Def
Amnesia
Rain Dance
Psychic
Toxic
This is my lead Pokemon, and the moves depend on the opponents team/lead. If they lead out with something that just wants to set up, I'll most likely toss up between Rain Dance/Toxic depending on the Pokemon out. If I think they're going to switch out, Psychic should be able to put on some damage no matter how small it may be. In the event they switch out, the next turn I will most likely set up a Rain Dance because my team orientates around it. If I feel like staying in I'll go for a Toxic or I'll switch out to an appropriate Pokemon. Amnesia is there just in case I Toxic a Pokemon and want to stall out a little. The good thing about this is that even if I take some damage, I would have set something up, and by switching out I'll get quite a substantial amount of HP.

Nacho Libre/Ludicolo
Modest +Sp. Atk -Attack
Swift Swim
Choice Specs
+168 Hp +252 Sp. Atk +88 Sp. Def
Hidden Power (Dragon)
Ice Beam
Surf
Giga Drain
I should be able to tempt different predictions from the opponent with Ludicolo because it can be a surprise package. It's has a good basis with Special Attack, and with Rain Dance up it's speed inceases quite a lot and it can become a sweeper. Giga drain is if I begin to loose too much health, while the rest are just for the damage depending on the different Pokemon. Hidden Power Dragon is there to surprise the opponent, and it's a fallback just in case a Fire type Pokemon comes out for some reason. But Ludicolo is really just my aggressive Pokemon.

E=MC2/Emolga
Hasty +Speed -Def
Static
Magnet
+4 HP +252 Sp. Atk +252 Speed.
Iron Tail
Agility
Thunder
Volt Switch
Emolga is my fast sweeper, but can also just become an annoyance. With a high speed stat, and agility, It can soon outspeed the majority of Pokemon out there. With Rain Dance up, Thunder can ultimately reek havoc to a lot of the Pokemon out there, even if it isn't super effective. Magnet also increases electric moves power by 20% which gives Thunder and Volt Switch an extra boost. Iron Tail is for those Rock Pokemon that come in thinking they can take out Emolga, even though it is Physical it should still do a substantial amount of damage, though this is kind of a last resort and I have many Pokemon I can switch out to to take the damage. Volt Switch is there to have Emolga pop in, and then pop out again while doing quite a lot of damage due to Magnet.

Arnold/Aggron
Brave +Atk -Speed
Heavy Metal
Choice Band
+140 Atk +224 Def +144 Sp. Def
Heavy Slam
Earthquake
Stone Edge
Thunder
An all out aggressive Physical attacker. By having Heavy Metal I think Heavy Slam's base attack is at 120 which is a big boost. Earthquake is there for those Pokemon with a weakness to ground. Stone Edge is also there for Pokemon that have a weakness to Rock, but also has a high crit ratio which is good if I just want to go for a couple of lucky sweeps. Thunder is there to work with Rain Dance which is also good to sweep out unsuspecting Pokemon. I am tossing up with Heavy Metal and Sturdy, mainly because the opponent can use Rain Dance against me, so I'm thinking of also swapping Heavy Slam for a different move as well.

Milotic/Milotic
Calm +Sp Def -Attack
Marvel Scale
Leftovers
+88 HP +212 Sp. Atk +208 Sp. Def
Rest
Sleep Talk
Surf
Dragon Pulse
Just the usual annoying staller, I equipped it with Rest and Leftovers just to extend the period I can keep it in the game. I gave it Sleep Talk so that the only two moves it can toss up between are Surf and Dragon Pulse, both very strong Special moves which compliment the build of this Milotic. This is one of the Pokemon in my team that don't have a complete build revolving around Rain Dance, it's there just to cause problems to the opponent and it's also a Pokemon I can swap into to take some damage.

Pelipper/Pelipper
Timid +Speed -Atk.
Rain Dish
Damp Rock
+164 HP +128 Sp. Atk +216 Speed.
Hydro Pump
Hurricane
Rain Dance
Agility
Really just a second Rain Dance set-up Pokemon, Damp Rock also increases the amount of turns Rain Dance stays up. I tried to turn it into a balanced Pokemon, Hydro Pump and Hurricane are strong moves aided by Rain Dance just in case I need to use this Pokemon offensively or just to get extra damage on before it turns into a fodder. Agility is also there to increase it's speed, and I think if I do that I can turn it into an all round Pokemon. But I'm still a bit confused about what to do with it.

A lot of criticism would be awesome, if you have the time of course.
This team is for Uber-restricted matches.

How about swapping Pelipper and making Politoad your lead;

Politoad @ Leftovers
Drizzle
Calm Nature
Ev's: 252 Hp | 4 Def | 252 Spe
Surf - Encore - Toxic - Ice Beam

Drizzle ability get permanant rain off the bat so you don't have have a wasted move, using encore cripples other leads trying to get rocks or whatever up. Toxic to annoy and Surf and Ice Beam for the good coverage. :)

Rain basically revolves around the concept of Drizzle and how to make it stay in. Since Drizzle is really that much more powerful in comparison to Rain Dance, I would recommend adding him to this team in place of Pelipper, just like ShinySalamence said. The standard Specially Defensive set could do. Next, you may want to swap out Audino for Cleric/WishPass Blissey (or Eviolite Chansey), due to its sheer amount of special bulk that allows it to take on some of the most fearsome threats in the metagame, including Thundurus, CM Landorus, Suicune, and basically anything that lacks a physical move. Alternatively, you could try Specially Defensive WishRachi who is exponentially much more useful than Blissey, especially taking into consideration its Serene Grace Paraflinching ability.

Next, I would recommend Vaporeon over Milotic due to its ability to take advantage of Water Absorb (which would void water attacks, useful due to this team's basing around Rain) and Hydration, which basically trolls everything that doesn't 2HKO Vaporeon. ;) With its titanic HP stat, excellent Special Defense and Acid Armor taken into the equation it makes for a very fearsome mixed tank after just one turn of set-up.

Aggron looks out of place on this team, if what you're looking for is Rock-type coverage then I would recommend Kabutops. Giving it a Choice Band with the Swift Swim boost on allows for an extremely heavy-hitting Waterfall due to rain's boost and the STAB bonus.

Emolga is an extremely underused pokemon, and for good reason. Its Speed is excellent, but nothing overwhelming. Moreover, its mediocre base SpA stat (75) won't be able to put a decent dent in anything, even with Thunder's huge base power and STAB bonus. If you're looking to abuse Thunder in the rain, consider replacing it with Thundurus, Jolteon or Zapdos. I would recommend Tornadlus in this spot though, since it helps solves numerous problems with defensive threats such as Blissey and her little sister (although sufficiently taken care of by Kabutops, it's never bad to have a back-up check).

On Ludicolo, I recommend taking it out for either Specs Kingdra or Shell Smash Gorebyss. Specs Kingdra hits a ridiculously high SpA stat, supported by a STAB Surf/Hydro Pump that gets the boost from the rain as well as STAB. Draco Meteor can also serve as a secondary STAB move that provides nearly unresisted coverage with Surf/Hydro Pump. The other two moves you can adjust to your liking, although I would definitely recommend Dragon Pulse to be one of them.

If you do end up following all these suggestions, be sure to put Politoed as the lead. Good luck with this team! ;)