In my side I carry cards that help with decks that I personally have issue dealing with based on my play style and decks. Soul release is my go to for annoying the crap out of lightsworn and d rulers. I also carry magic deflector to handle noble knights, fire fist, and slow down fire king and prophecy (locking prophecy out of wisdom, tower, hall, life, and fate screws with them a lot more than you'd expect) I usually switch off between shadow-imprisoning mirror and consecrated light depending on how vital normal summons are to the deck, as consecrated eats it up. If the deck itself is dark I will then use imperial iron wall, as my dark deck of choice is currently ghostricks and banishing my little ghosties is very not okay. It also works well against prophecy, not allowing high priestess to activate her effect to destroy, which is one of their main forms of offense. Finally the last two slots of 3 in my side go to decks I see primarily at my local tournaments when one of the guys there gets mad and tries to use annoying decks to win:nature's reflection and droll & lock bird, for burns and exodia respectively. Before droll and lock my exodia killer of choice was exchange, to steal a piece and make the win condition impossible.
CS awarded