Gengar ex is intriguing and has a few combos.
Poltergeist is good for the cost. PC for 40 is already
good, but it adds 10 more for each trainer in the opp's
hand. Versus a good deck, against a good player who is
watching their trainer size to make sure it doesn't get too
big, Poltergeist should do about 70 damage which is great.
Now look at Prize Taunt. PPC for 60 is already great, but
if you are losing in terms of prize count, it does 100!
Resistance to colorless? Haha take that Dunsparce!
Unlimited - A few combos with this. Since his third attack
does better if you are losing, what better way to give your
opponent prizes than Electrode? (Base Electrode and
Electrode ex would both work, they have their pros and cons,
but I prefer base electrode for this). You can explode a
base Electrode, attach it to Gastly and have it provide 2
Psychic, attach another energy, rare candy to Gengar ex, and
do turn 1 100 damage. If your opponent thinks he's slick by
SERing your Gengar ex, you do the Electrode trick again and
get powered up in 1 turn. Not that hard with Computer
Search and Oak.
You can also tech in a couple Expedition Gengar, to put your
damage on to your opponent. That will make sure he hardly
ever gets knocked out. While your at it you could throw in
Team Magma Hideout. When you play your Pokemon they will
take 10 damage, which you can then use exp gengar's power to
move them over to the oppponent's. 4/5
Modified(RSon) - It's not as good here as it is in
Unlimited. Giving your opponent 2 prizes with Electrode ex
will suck. You could use it without Electrode though and
use it for its Poltergeist. It should do a decent amount of
damage with that. I just don't like Gengar ex in this
format because it doesn't do a huge amount of damage like
other ex pokemon can do. 2/5
Limited - You got a couple Gastly(yay) and Haunter? Take
it. Even if you only get a 1-1-1 line, still take it. The
chance of one of them being prized are slim. Gengar ex is
very helpful so take it ok? 4/5