*cheers* SOMEONE REMEMBERS BLOWBACK DRAGON! W00T! (but in my opinion, luck shouldn't exist for top 10... sorry)
ahem...
Yugioh Top 10 (in no particular order)
Wave Motion Cannon
-pwnage to the extreme... not that many cards in the game has such attention grabbing charm that can redirect all Breaker the Magical Warrior and Mystical Space Typhoon from the facedown Call of the Haunted to this card instead. It makes stall decks shiver in fear, and greatly disrupts the momentum of any opposing player's strategy at the sight of this. It forces the player to think "either I kill that thing or that thing kills me." Its unwritten side effect is simply unmatched.
Cyber Dragon
-do I *really* have to explain...
Return from the Different Dimension
-this card itself makes many other cards usable. What you think is "excellent" cannot be so good without this card to combo with it, really (Bazoo, partially Strike Ninja, and the entire RFG deck type)
Mobius the Frost Monarch
-destroys the entire magic/trap back row, and 2400 attack power? *surrenders*
Reinforcement of the Army
-honestly, warriors can't even be half as strong as they are today without this ultimate searcher in the game. It's better than Witch of the Dark Forest (for warriors) because it doesn't even cost a summon to use it... It's deadly because the owner can call upon a heck of a wide selection according to the situation. Need monster removal? D. D. Warrior Lady or Exiled Forces. Need hand disruption? Don Zaloog. There's a solution to a lot of situations in this card.
Heavy Storm
-mass spell destruction... name me a deck that doesn't use this >>; (K if even Exodia decks pack one, it's saying quite a bit)
Call of the Haunted
-recursion is always helpful... only inferior to the one below
Premature Burial
-recursion in its ultimate form excluding bans
Mystical Space Typhoon
-it's one of the staples out there... and it will save lives by destroying a Premature Burial in the nick of time.
Sacred Phoenix of Nepthyrs
-regardless of how much I trash this thing, it has its strength, because not all decks are cookie cutters with their 3 D. D. Assailant running around with Bottomless Traphole, and Phoenix will eat anything alive that doesn't uses cooke-cutter decks or Chaos Sorcerer decks.