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
with master baLL
you can trade a Pokemon from black or white holding a 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
only in Pokemon white by urself if u have master ball!
professor juniper gives it to you
The Professer will give it to you after the last gym