gengar

[peter1994]

Which would be better to use in singles and doubles

Gengar has three good sets, really:
-Shadow Ball
-Sludge Wave/Sludge Bomb
-Focus Blast
-Destiny Bond/Taunt/Substitute
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb/Focus Sash/Black Sludge

or
-Substitute
-Shadow Ball
-Will-o-Wisp
-Taunt/Sludge Bomb/Sludge Wave/Disable
Nature: Timid
EVs: 28 HP/148 SAtk/80 SDef/252 Spe
Item: Black Sludge

or
-Hex
-Taunt
-Will-o-Wisp
-Sludge Wave/Sludge Bomb/Substitute
Nature: Timid
EVs: 8 HP/248 SAtk/252 Spe
Item: Black Sludge