Hmmm...comp. search is the best single trainer in the game, 'cause you can get ANY card you need at that time in the game. If you need an oak, get it. If your opp. has a handful of cards and you need to, it to get that copycat. In other words, it can be any of the other trainers, or the poke you need, or the nrg you need. Timing is everything in the game, if you get the card you need when you need it, you will most likely win the game. Now in modified, copycat and oracle are very close, if you pair an oracle with a bill, that's better than even a comp. search in any enviroment. You don't have to discard any cards, and you get 2 of any card you need. That almost always is a game breaker. But thats not a single card, so in modified, i guess copycat takes a small edge over elm or oracle.