I second this. Blizzard, Giga Drain, HP Fire.
If you plan on using a physical attack for your last move, use a Hasty nature, so that you don't get an Attack drop. Then Ice Shard and Wood Hammer become viable options (though Ice Shard + Choice Scarf is slightly redundant).
You could also consider Grass Knot, as a few Pokemon are hit harder by it than Giga Drain (Against Tyranitar, Terrakion, Gigalith, Rhyperior, and Mamoswine specifically, Grass Knot is Abomasnow's strongest attack, even over Blizzard), but then you wouldn't be healed by Giga Drain either.