Yamask / Cofagrigus
Training tip: Here's how Mummy works: any time the user makes contact with an opponent either by hitting or being hit with a contact move, the opponent's Ability changes to Mummy for the duration of the battle, effectively neutralizing its own ability. Also worth noting, Cofagrigus not only has the highest defense of any Ghost-type to date, but it has the highest defense of any Unova Pokemon. Its speed is dismal though, so it might be worth considering a Trick Room (TM92) moveset to turn that to your advantage.
Frillish / Jellicent
Continuing the tradition of dual Ghost-types with unique typing, Frillish and Jellicent are the first and only Water/Ghost types in the game. Each has two distinct forms, with color schemes reminiscent of Shellos and Gastrodon from Diamond/Pearl, but Frillish and Jellicent's forms are determined by gender rather than locale. Their jellyfish-like appearance my look non-threatening, but just like real jellyfish they can pack a serious sting. Like Yamask, Jellicent's Pokedex entry, which basically claims that it will kill anyone who crosses its path, is horrifying enough to qualify it as one of the creepiest Pokemon of Black and White.
Training tip: Both of their regular abilities are formidable, and Cursed Body is new, so it's definitely worth trying out – with a 30% chance of disabling any attack used against it, it definitely has the potential to be annoying. They both only learn special attacks via level up, so it's easy to stick to what they're good at. New move Scald (TM55) is a good choice because it takes advantage of their special attack and adds the possibility of inflicting a burn.
Litwick / Lampent / Chandelure
Another evolutionary line with completely new typing, this dual Ghost/Fire three stage family is easily one of the coolest new Unova Pokemon gameplay-wise. Litwick starts as an adorable little smiling candle with wax covering one eye, and ultimately ends up as Chandelure, a terrifying chandelier with the highest special attack of any non-legendary Pokemon. Like all proper Ghost-type Pokemon, Chandelure is all about death, and its known to suck out its victims' souls and leave nothing but the charred husk of a body behind.
Training tip: If you EV train in special attack and speed, Chandelure has the potential to be a formidable special sweeper. Will-o-wisp (inflicts burn) and Hex (does double damage when opponent is burned, plus since it's a Ghost-type move Chandelure gets a STAB) also make a great moveset combo.
Golett / Golurk
With yet another unique typing (are you seeing a pattern here?), Golett and Golurk don't conform to the typical creepy, morbid design of most Ghost-type Pokemon. With their heavy suits of armor and ultra-high attack stats (Golurk has the highest attack stat of any Ghost-type), they're said to use their power to protect all people and Pokemon. Oddly enough, despite its Ground-type, Golurk can also fly through the sky at mach speeds.
According to Game Freak (via Bulbapedia), Golett and Golurk are the first Pokemon ever to be designed by a westerner, British designer James Turner. Along with Golett and Golurk, he also designed four other Unova Pokemon: Vullaby, Vanillite, Vanillish and Vanilluxe.
Training tip: Golett and Golurk's Ground/Ghost combo give them three immunities to Normal, Fighting, and Electric. Golurk is a pure physical attacker, and with its Iron Fist ability, Focus Punch is a must, which Golett learns at level 55 and Golurk learns at level 70. Even though it doesn't get a STAB, Focus Punch's base power of 150 plus the 20% Iron Fist bonus make it a good choice for any Golurk moveset.
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