Nidoqueen/Gengar, or "Mother Gengar" has won a TON of BRs, along with Infernape 4 and Speedrill. Nidoqueen makes it nigh impossible to KO a G'ed Gengar without activating Fainting Spell. Also, as stated above, all these said "Counters" to Gengar's different abilites look a lot easier on a thread then in an actual game. You say Uxie? Gengar says Thxkbai Shadow Room/Crobat. In order to really beat down Gengar, you have to
a) G anything with a power to avoid free prizes
b) Clear hand of Trainers to avoid a Poltergeist OHKO.
c) Find a consistent way around Fainting Spell, made a heck of a lot harder by Nidoqueen.
Most players can do an average of one-two of these things, the only time I saw a guy do all three was when he had an active Flygon SW with an Unown G and a Devoluter with a G'ed benched Claydol and a benched Nidoqueen, keeping his hand at one to two cards. ROFLMAO.
Anyway, to stay on topic, I think Gengar is an excellent choice for Nats, mostly because people walk in with 2 Unown G and think they will be fine.:biggrin: