http://www.smogon.com/dp/pokemon/gengar
Pretty minor edit, just doing a little work on the Scarf set.
[SET]
name: Choice Scarf
move 1: Hidden Power Ice
move 2: Shadow Ball
move 3: Focus Blast
move 4: Thunderbolt
item: Choice Scarf
nature: Modest / Timid
evs: 4 HP / 252 SpA / 252 Spe
[SET COMMENTS]
<p>Odd though it may seem to use Choice Scarf on something as fast as Gengar, this set has some very alluring advantages. Gengar's varied movepool lets him act as an effective revenge killer against some of the biggest threats in D/P; Tyranitar, Azelf, Salamence, Garchomp, and Gyarados (including bulky varieties) will all fall in one hit to their corresponding moves without significant defensive investment. Scarf Gengar is by no means a counter to such Pokemon, but it can easily save you the match should you make an error and let your Gyarados counter be KO'd by Pursuit.</p>
<p>If your team already has sufficient coverage against one of the aforementioned threats, feel free to swap an attack out for Hypnosis or Destiny Bond, which give Gengar the capacity to stop most other opponents in their tracks. Explosion (preferably used with a Mild or Hasty nature) allows you to revenge kill a large number of Pokemon with one move as well, but don't expect to beat Blissey without a significant amount of investment in Attack or some previous damage. Timid nature might seem like true overkill, but it does let you get the jump on other Scarf Gengars or anything sitting just above. Since most Pokemon near that Speed level will be fragile enough to be defeated in one hit, possessing a Speed advantage can frequently net you a surprise KO. You maintain all the aforementioned OHKOs as well (with the exception of Garchomp, who has less than a 20% chance to survive Hidden Power Ice), so Timid is definitely worth consideration. </p>
Pretty minor edit, just doing a little work on the Scarf set.
[SET]
name: Choice Scarf
move 1: Hidden Power Ice
move 2: Shadow Ball
move 3: Focus Blast
move 4: Thunderbolt
item: Choice Scarf
nature: Modest / Timid
evs: 4 HP / 252 SpA / 252 Spe
[SET COMMENTS]
<p>Odd though it may seem to use Choice Scarf on something as fast as Gengar, this set has some very alluring advantages. Gengar's varied movepool lets him act as an effective revenge killer against some of the biggest threats in D/P; Tyranitar, Azelf, Salamence, Garchomp, and Gyarados (including bulky varieties) will all fall in one hit to their corresponding moves without significant defensive investment. Scarf Gengar is by no means a counter to such Pokemon, but it can easily save you the match should you make an error and let your Gyarados counter be KO'd by Pursuit.</p>
<p>If your team already has sufficient coverage against one of the aforementioned threats, feel free to swap an attack out for Hypnosis or Destiny Bond, which give Gengar the capacity to stop most other opponents in their tracks. Explosion (preferably used with a Mild or Hasty nature) allows you to revenge kill a large number of Pokemon with one move as well, but don't expect to beat Blissey without a significant amount of investment in Attack or some previous damage. Timid nature might seem like true overkill, but it does let you get the jump on other Scarf Gengars or anything sitting just above. Since most Pokemon near that Speed level will be fragile enough to be defeated in one hit, possessing a Speed advantage can frequently net you a surprise KO. You maintain all the aforementioned OHKOs as well (with the exception of Garchomp, who has less than a 20% chance to survive Hidden Power Ice), so Timid is definitely worth consideration. </p>