I've been playing around a lot with hail recently, as I feel like weather is useful in this metagame to counter the other weathers running around, and because hail is the least frequently used, so it's generally the least prepared for. After testing a few different builds, I settled on the core of Abomasnow, Tentacruel, and the real star of this team, Froslass. I chose the rest according to symmetry and to work as a semi-stall sort of team. So here's a first look at the team-
Abomasnow@Leftovers-Snow Warning
Sassy-252 HP/172 Def/84 SpDef
Leech Seed
Substitute
Protect
Blizzard
Abomasnow serves the invaluable purpose of starting the hailstorm, and is actually serves the purpose of out-stalling certain walls such as Blissey and Ferrothorn. It also is able to set up leech seed or land a free blizzard on something after stalling out one Pokemon. I generally lead with it as long as the other team doesn't have a weather starter.
Froslass@Leftovers-Snow Cloak
Timid-252 Speed/252 Sp Atk/4 Def
22 HP IVs
Substitute
Blizzard
Thunderbolt
Disable
This is my single favorite Pokemon in Gen 5. Max speed allows it to outspeed 95% of the OU metagame, 252 Sp Atk allows it to pack a punch, and 22 HP IVs bring it to 272, which is divisible by 16, a nice leftovers divisible number. You can opt for 20 HP EVs and 31 IVs if you'd like, but Froslass never really gets hit by anything and you lose power, so there's really no reason to do that. The idea is to pop in with hail on the field, and proceed to clean up anything slower. Here's a typical example of how it works-
Vs. Lucario: Set up a sub as they crunch. Use disable. T-bolt as they decide to either stay in and die or switch to something to take the TBolt. Say they switch to Scizor and get hit. Use disable on the turn they bullet punch. They are either out of moves due to a choice set or must take another hit and use a slower move.
Keep in mind that on each turn, they are taking hail damage, and there is always the chance for them to miss due to snow cloak. This also renders moves like stone edge, hurricane, and thunder basically useless. It basically nets an automatic KO on anything slower, and the BoltBlizz combo deals serious damage to everything but Magnezone and Rotom-H I believe.
Tentacruel@Black Sludge-Liquid Ooze
Bold-252 HP/240 Def/16 Spe
Knock Off
Toxic Spikes
Rapid Spin
Surf
Always a hail team staple. It spins away hazards, it sets up toxic spikes to wear down their team quickly with the hail, and it knocks off their leftovers to speed up this process. It has wonderful synergy with ice type Pokemon, and it carries surf to threaten taunt users and dent anything weak to it. Quite often I'll get locked into a hazard war against an opposing Ferrothorn or Forretress, and of course Tentacruel always wins.
Terrakion@Choice Scarf-Justified
Adamant-252 Atk/200 Spe/28 Def/28 Sp Def
Close Combat
Stone Edge
X-Scizzor
Sacred Sword
This dude is my rock resist, my third fire resist, and my revenge killer. Since few Pokemon resist his monstrously powerful CC, he can sweep teams easily with just this one move once the resists are eliminated. It's great against any opposing scarfers, outspeeding anything slower than adamant scarfed Landorus, adamant Mence, and Dnite after one DD, and all Gyara, Scrafty, and Volcarona after one DD/QD. It's also great at taking out Lati@s with X-Scizzor.
Heatran@Leftovers-Flash Fire
Calm-252 HP/252 Sp Def/4 Def
Stealth Rock
Fire Blast
HP Ice
Roar
My defensive stealth rocker. It provides valuable resistances, hits pretty hard, frightens sun teams, and is able to lay down stealth rock with relative ease. It takes dragon type moves like a beast and can KO back with HP Ice. It's able to deal large chunks of damage and force lots of switches/roar to rack up stealth rock damage and spread toxic spikes around.
Sigilyph@Flame Orb-Magic Guard
Bold-252 HP/200 Def/56 Sp Atk
Psycho Shift
Roost
Cosmic Power
Stored Power
Everybody hates this thing. Its purpose is to wall fighting types, which it does wonderfully. It's also a great damper to physical dragons, Scizor, or anything else immune to toxic spikes that won't enjoy a burn. It really helps out with being immune to stealth rock and hail damage also. Cosmic Power allows me to set up on anything like Ferrothorn or Forretress that can't fight back. It also survives any TTar attack after one cosmic power and full health, so the burn is guaranteed.
Last Look-
So that's the team. The idea is to weaken the enemy team and set up enough hazards so that Froslass can take out the bulk of their Pokemon with its dastardly tricks. It has been very successful so far, and is a lot of fun to use. Leave any suggestions or comments that you'd like to share. Thanks in advance!







Abomasnow@Leftovers-Snow Warning
Sassy-252 HP/172 Def/84 SpDef
Leech Seed
Substitute
Protect
Blizzard
Abomasnow serves the invaluable purpose of starting the hailstorm, and is actually serves the purpose of out-stalling certain walls such as Blissey and Ferrothorn. It also is able to set up leech seed or land a free blizzard on something after stalling out one Pokemon. I generally lead with it as long as the other team doesn't have a weather starter.

Froslass@Leftovers-Snow Cloak
Timid-252 Speed/252 Sp Atk/4 Def
22 HP IVs
Substitute
Blizzard
Thunderbolt
Disable
This is my single favorite Pokemon in Gen 5. Max speed allows it to outspeed 95% of the OU metagame, 252 Sp Atk allows it to pack a punch, and 22 HP IVs bring it to 272, which is divisible by 16, a nice leftovers divisible number. You can opt for 20 HP EVs and 31 IVs if you'd like, but Froslass never really gets hit by anything and you lose power, so there's really no reason to do that. The idea is to pop in with hail on the field, and proceed to clean up anything slower. Here's a typical example of how it works-
Vs. Lucario: Set up a sub as they crunch. Use disable. T-bolt as they decide to either stay in and die or switch to something to take the TBolt. Say they switch to Scizor and get hit. Use disable on the turn they bullet punch. They are either out of moves due to a choice set or must take another hit and use a slower move.
Keep in mind that on each turn, they are taking hail damage, and there is always the chance for them to miss due to snow cloak. This also renders moves like stone edge, hurricane, and thunder basically useless. It basically nets an automatic KO on anything slower, and the BoltBlizz combo deals serious damage to everything but Magnezone and Rotom-H I believe.

Tentacruel@Black Sludge-Liquid Ooze
Bold-252 HP/240 Def/16 Spe
Knock Off
Toxic Spikes
Rapid Spin
Surf
Always a hail team staple. It spins away hazards, it sets up toxic spikes to wear down their team quickly with the hail, and it knocks off their leftovers to speed up this process. It has wonderful synergy with ice type Pokemon, and it carries surf to threaten taunt users and dent anything weak to it. Quite often I'll get locked into a hazard war against an opposing Ferrothorn or Forretress, and of course Tentacruel always wins.

Terrakion@Choice Scarf-Justified
Adamant-252 Atk/200 Spe/28 Def/28 Sp Def
Close Combat
Stone Edge
X-Scizzor
Sacred Sword
This dude is my rock resist, my third fire resist, and my revenge killer. Since few Pokemon resist his monstrously powerful CC, he can sweep teams easily with just this one move once the resists are eliminated. It's great against any opposing scarfers, outspeeding anything slower than adamant scarfed Landorus, adamant Mence, and Dnite after one DD, and all Gyara, Scrafty, and Volcarona after one DD/QD. It's also great at taking out Lati@s with X-Scizzor.

Heatran@Leftovers-Flash Fire
Calm-252 HP/252 Sp Def/4 Def
Stealth Rock
Fire Blast
HP Ice
Roar
My defensive stealth rocker. It provides valuable resistances, hits pretty hard, frightens sun teams, and is able to lay down stealth rock with relative ease. It takes dragon type moves like a beast and can KO back with HP Ice. It's able to deal large chunks of damage and force lots of switches/roar to rack up stealth rock damage and spread toxic spikes around.

Sigilyph@Flame Orb-Magic Guard
Bold-252 HP/200 Def/56 Sp Atk
Psycho Shift
Roost
Cosmic Power
Stored Power
Everybody hates this thing. Its purpose is to wall fighting types, which it does wonderfully. It's also a great damper to physical dragons, Scizor, or anything else immune to toxic spikes that won't enjoy a burn. It really helps out with being immune to stealth rock and hail damage also. Cosmic Power allows me to set up on anything like Ferrothorn or Forretress that can't fight back. It also survives any TTar attack after one cosmic power and full health, so the burn is guaranteed.
Last Look-
So that's the team. The idea is to weaken the enemy team and set up enough hazards so that Froslass can take out the bulk of their Pokemon with its dastardly tricks. It has been very successful so far, and is a lot of fun to use. Leave any suggestions or comments that you'd like to share. Thanks in advance!