Definitely Thundurus. You can get 2 Master Balls in Black and White. You should save the second one for shinies or event pokemon.
the master ball is for zekrom in white and reshiram in black
yes, you can catch ANY pokemon with a master ball, reshiram is who it is aimed at in white 2
you can trade a Pokemon from black or white holding a master ball.
with master baLL
Yes you can I have done it
don't have the game
After defeating Cyrus in Veilstone, he should give a Master Ball to you.
giratina
In white you use the master ball in black you trade
master ball or get power low
Throw a Master Ball at it.
only in Pokemon white by urself if u have master ball!