If I use Gengar's "Cursed Drop" attack, can I put damage counters on more than one of my opponent's Pokemon, or do I have to put all four counters on one Pokemon?
You can put the 4 damage counters on their Pokemon in any way that you like.
Source:
Triumphant FAQ (2010-11-04), PUI Rules Team (2010-11-04)
When using Rotom's "Plasma Arrow" attack, I get to choose one of the opponent's Pokemon and do 20 damage for each Energy attached to it; but do I do the damage to the Defending Pokemon, or to the Pokemon I chose?
To the Pokemon that was chosen. If the damage were to be done to the Defending Pokemon, there would be a "20x" value in the damage field of the attack.
Source:
Undaunted FAQ (2010-09-09), PUI Rules Team (2010-09-09)
What happens if one of the players doesn't have a benched Pokemon when using Drifblim's "Take Away" attack?
There is no restriction on using the attack if there is no benched Pokemon. If a player has no Benched Pokemon, that player loses. If neither player has Benched Pokemon, then it is a tie and a game of Sudden Death must be played.
Source:
Undaunted FAQ (2010-09-09), PUI Rules Team (2010-09-09)
Can Espeon's "Solar Suggestion" attack place damage counters onto a Jolteon that can't be hit by effects due to a successful coin flip during its "Agility" attack, or onto a Toxicroak [G] with its "Anticipation" Poke-BODY enabled? If I can't place them, what do I do with the damage counters I removed from my Pokemon?
You cannot place damage counters onto that Jolteon or Toxicroak [G], but you can still remove damage counters from your own Pokemon. If you select a Pokemon under the status of not receiving effects, the damage counters that would be placed onto that Pokemon simply disappear from play.
Source:
Undaunted FAQ (2010-09-09), PUI Rules Team (2010-09-09)