A fun (although admittedly gimmicky) set involves the use of Toxic Spikes and Venoshock:
Dragalge with Black Sludge
EVs: 252 SpA, 252 HP, 4 Def
Ability: Adaptability/Poison Point
-Venom Drench/Dragon Tail/Focus Blast/Hydro Pump
The set works like this: Toxic Spikes is used to spread poison everywhere. If the opponent is poisoned, Venoshock has the same power as Draco Meteor, except without the Special Attack drop. With Adaptability, this hits extremely hard, being able to OHKO 252 HP / 0 Def Clefable and outdamaging Latios. Draco Meteor is used as an alternate STAB and is preferred if the opponent is not poisoned. The fourth move is really your choice. Venom Drench cripples a poisoned opponent if you can't KO or heavily damage it with Venoshock. Dragon Tail can be used to shuffle opponents around and spread poison, although the negative priority means that Dragalge will be taking some hits. Focus Miss can be used to hit Steel-types who otherwise wall Dragalge completely. Hydro Pump is good if you want a more accurate coverage move.