Mine is EV trained in Attack. It knows:
Avalanche: Decent damage, works well with Curse, Wailord doesn't have that great of Speed, high accuracy, used to deal with Grass types.
Curse: Increases Attack stat and its low Defense stat. Decreases Speed to help Avalanche.
Earthquake: High power, high accuracy, double damage against Pokemon using Dig, used to deal with Electric types.
Waterfall: Good power, high accuracy, STAB, decent chance to cause flinching.