Well, I prefer Ice Punch on Weavile, and for a few reasons:
-Weavile is already faster than Hydreigon, even if he uses Adamant and Hydreigon uses Timid, and Adamant Life Orb Ice Punch does 76.6%-90.43% to 6 HP Hydreigon. I used Hydreigon because you mentioned him in your post.
-Ice Punch is his strongest Ice-type physical attack, barring slow Avalanche, and Weavile is obviously NOT slow.
This is for Weavile, I didn't quite get if you were talking about Abomasnow or Weavile. For Abomasnow, I guess use Blizzard, since he can abuse it under Hail. Ice Shard is for priority, and I wouldn't use it for any other reason.