Here is a few Pokemons that work in hail:
Abomasnow @ Choice Scarf
Ability: Snow Warning
EVs: 252 Spd / 252 Atk / 4 SAtk
Hasty Nature
- Wood Hammer
- Blizzard
- Earthquake
- Ice Shard
You can't have hail without Snow Warning, and Abomasnow is the only viable user of it. That said, it dosnt need to run a defensive set, but is more than capable to run all out attack. However, its stats are still subpar, so it works better in the lower tiers or as a late game sweeper.
Kyurem @ Choice Scarf
Ability: Pressure
EVs: 252 Spd / 252 SAtk / 4 SDef
Timid Nature
- Blizzard
- Dragon Pulse
- Earth Power
- Focus Blast
There is nothing as terrifying in the Hail as Kyurem. Regardless of its form, this dragon is a beast, sporting great offensive typing and great stats. Any of the three forms are lethal in Hail, albeit Kyurem-W is banned from OU, and Kyurem-B prefer a mixed set to fully abuse its 170 Atk.
Froslass @ Focus Sash
Ability: Cursed Body
EVs: 252 Spd / 252 SAtk / 4 SDef
Timid Nature
- Blizzard/Ice Beam
- Spikes
- Destiny Bond
- Shadow Ball/Taunt
Less of a sweeper and more of a utility Pokemon. It's great natural speed allows it to easily set up Spikes, and then revenge kill with Destiny Bond. This means it doesn't have to be the hardest hitter to do some damage, but rather just the fastest.
Arcanine @ Choice Band
Ability: Flash Fire
EVs: 252 Atk / 252 HP / 4 SDef
Adamant Nature
- Flare Blitz
- Wild Charge
- Crunch
- Close Combat
With all these special Ice types running around, you will need to protect them any way you can. Arcanine's Flash Fire allows it to check multiple Pokemon that threatens Abomasnow and CO. Basically every Hail team will need a Pokemon to take a Fire Attack, and Arcanine, Chandelure and bulky Water types such as Vaporeon are the most common.
Alakazam @ Focus Sash
Ability: Magic Guard
EVs: 252 Spd / 252 SAtk / 4 HP
Timid Nature
- Psyshock
- Shadow Ball
- Focus Blast
- Energy Ball
Albeit having nothing to properly abuse the Hail, Alakazam's Magic Guard leaves it unaffected by Hail, which is always a nice thing. If you need something else than Ice types, Kazam is your guy.