Thunderbolt, Psychic and Giga Drain offer little to poor additional coverage so have little justification warranting a place on any set imo. Sludge Wave, Focus Blast and Substitute, Taunt or Destiny Bond @ Black Sludge, Fightinium Z or Life Orb are better. Focus Blast is necessary to OHKO Dark-types such as Hydreigon, Krookodile, and Bisharp. It can also be used with Fightinium Z to have a powerful, perfectly accurate Fighting-type move. Sludge Wave hits the fairy types that are common place, it also a nice secondary STAB move. Sub is useful to scout switch ins, especially those with Pursuit or scarfers. Taunt shuts down walls whilst Destiny Bond can grab you a quick kill.
A bulkier gengar set with sub, pain split, hex and will-o-wisp is also cute and annoying.
† Are you going to Scarborough Fair?
Yesterday holds memories in time
Remember me to the one who lives there
She once was a true love of mine †