1)Blue Eyes White Dragon
Not my favorite but were talking about cards that could dominate.  Obviously 
it is a very rare card and the most powerful single card.  Top it off with 
some magic cards and it's the best

2)Monster Reborn 
It is so obvious, lets you bring back a monster as a zombie, any monster and 
put it under your control

3)Red Eyes Black Dragon
A very powerful card fused by Palmerization makes an incredible fighting 
machine even by itself it is capable of taking good cards out.

4)Dark Magician
Very powerful card, one of my personal favorites great attack and defence 
except for the 2 tributes he is still 4th in line

5)Change of Heart
More like a miniature Monster Reborn it lets you take one of your opponents 
Monsters for your own but unfortunately its limited 1 per deck.

6)De-Spell
Lets you take out a Magic Card, which would mean victory in most cases, 
bringing a a monsters power down for the kill.

7)Man Eater Bug
Shouldn't take many points off of you when it dies but it will let you take a 
Blue Eyes right out of the picture.

8)Swords of Revealing Light
Freeze your opponent for three turns gives you enough time to improve your 
monster or something.

9)Palmerization Card
If you can fuse two cards than it is great but it also kinda sucks because 
all cards aren't able to fuse, they should have some kind of fusion rules for 
this type of thing.

10)Red Medicine
Great Card in any case, but increasing your life points by 500 is great.