Best Decks?

Blackwings and Lightsworns are your best bet

That's true, but I always say use what you're comfortable with. If blackwings or lightsworns don't work the way you like (I deck out too often with Lightsworns) try something else. Personally, I love using fiends. Dark Necrofear and some Necrofaces rock.

hehehe........i have a deck that can finish the duel in one turn it requires Exodia on it that's the only tip i can give you hehehehe..................

If you like synchro monsters, try synchron deck
or naturia deck can be good to because it's synchros could negate the effect of magic and trap
Warrior deck's nice to?

Most difficult opponents in my opinion (with deck type):

Anca (Remove from Play)
Crow (Blackwing)
Naomi (Lightsworn)
Simon (Highlander)
Disa (Macro Monarch)
Bright (Fast Burn)
Reyna (Zombies)

Well, If you looking for easy-to-get and useful, try a defensive deck like Luna's.

Using Monster like Bowganian or Solar Flare Dragon to deal damage;
Golem Sentries, Swarm of Scarabs for monster controls;
Messenger of Peace, Level - Limit B, Swords of Revealing Lights, Nightmare's Steelcage and Wall of Revealing Light for repelling possible attacks;
Dark bribe, Judgment of Anubis, My Body as Shield for protections against card destroyer like Mystical Space Typhoon.

Well basically you focus on defenses, restricting enemy and yourself for attacking each other while dealing damage with bowganians, recovering LP with dancing fairies. The problem about this deck is, AI partner will try to attacks when there is an opening on enemy defenses which will mostly ended up all monster ram on traps like Mirror Force if you don't have counter spells or traps that helps you.
Another problem about this deck is when bioni...(i forget the name) the ice barrier dragon with the effect of discarding cards to return cards on the field, some traps to counter this kind of monster should be consider too.

oh i just notice this questions is asked last year lol...

I have a very nice burn deck which has worked wondrously for me since the time they created Gravity Bind and Level Limit Area - B :D. I'll just say what cards you'd need for this deck, the amount will depend on how you like it:

I cant give you a detailed description of this deck because I do not have my PSP handy lol. *Sorry* It will work though, trust me.

=Non-tribute Monsters=
Marshmallon
Spirit Reaper
Metal Golem the Moving Fortress
Obsidian Dragon
Stone Statue of the Aztec
Roulette Barrel
Stealth Bird
Golem Sentry
Swarm of Locusts
Swarm of Scarabs
+
(Some other lvl 1-4 monsters with 2000 DEF or more)
(Some other monsters which let you flip them into facedown def position before you end turn)
(Some monsters that protect your continuous traps or spells)
(Some monsters which let you retrieve spells or traps from the graveyard)
(Some other with the "cannot be defeated by battle" effect like Spirit Reaper)

=Tribute monsters=
Guardian Sphinx
Satellite Cannon
Lava Golem

=Spells=
Wave - Motion Cannon
Level Limit - Area B
Messenger of Peace
+
Chorus of Sanctuary
Stumbling
Yellow Luster Shield
The Dark Door

(Cards which let you add a specific card from your deck to your hand like Different Dimension Capsule)
(Some spells which let you retrieve spells or traps from the graveyard)
(Some spells which help you protect your own spells or traps)

=Traps=
Gravity Bind
Needle Wall
Ojama Trio
+
(Some traps that will let you return spells or traps from the graveyard)
(Some traps that will let you protect your continuous spells or traps on the field)

-----------------------------------------------------------------------
I shall now explain the use of these cards for this burn deck.

-High def monsters: use to stall for turns if you do not have stall spells like Messenger of Peace on your field.
Marshmallow and Spirit Reaper work as well.
Satellite Cannon works similarly, but more costly and bit riskier.

-Stall spells+traps: like Gravity bind, stop your opponents' attacking monsters.
You probably dont need swords of revealing light; it's overshadowed by level limit - area B

-Def aid spells: Like Chorus of Sanctuary, increase your monster's Def, keep them alive, not required.

-Monsters and spells+traps control: Roulette Barrel, Needle Wall, Swarm of Scarabs will terrorize your foe's monster zones. Swarm of Locusts will be enough to control his/her spell+trap zones. Ojama Trio will also do wonders (2 of these with a swarm of scarabs and your opponent almost cannot summon anything useful)

-Spells or traps protection cards: obviously, use these to protect your stall spells.

-spell or traps retrieving cards: Your opponent will get uber mad with your stall spells and traps, so they will try to destroy them, lucky you have these cards :)

-Return!: Each turn, flip your Guardian Sphinx up, all monsters under your opponent control will return to his/her hand. Nice, isnt it? I just love doing this ;). Golem Sentry works similarly, but one at a time.
*Remember, Ojama Trio will be destroyed under return effect.

-BURN!!!: Stealth bird and Wave - motion cannon will be your main attack force. Seriously, under the protection of stall spells like gravity bind, your stealth bird and your cannon spell will have your opponent cry Life Points lol. If you have 2 birds, each turn, he/she will lose 2000 LP. With the cannons on, you can deal some ~4000 damage to your opponent.
Lava Golem helps as well, but it's probably overkill.

There, you have the basic idea. You might win in 4 turns if you're lucky. Sometimes 7.
This deck can deal with almost ANY deck in the game. (Other plays might find a way around it, maybe with Jinzo, Frost Monarch or the like, but I ensure you, you will with a lot with this deck!)

Under similar strategies involving Gravity Bind, Level Limit, and Messenger of Peace, you have a variety as well. I will not say in detail, but I will give you a hint:

1. Life Points deck: use life points increasing cards and cards that will decrease your opponent LP whenever you get some.
(Use Spring of Rebirth in combo with Guardian Sphinx, Golem Sentry, and Penguin Soldier.)

2. Exodus Deck: Use some card retrieving cards, Reload, and the like will work.

3. Final Countdown deck: use some LP increasing cards along with 3 "Final Countdown". After 20 turns stalling your opponents, you win.

4. Spirit Message: Put as many "Spirit Message" cards in your deck as possible. Use some spells or traps retrieving cards. Also use cards that will let you destroy your own spells or traps (to destroy gravity bind and level limit when you needs space for a Spirit Message card.

5. Skull Servants: Have 3 skull servants and 3 King of the Skull Servants in your deck. Use the trap that lets you toss cards with the same name from your deck to your graveyard. After you have used this trap, your King of the Skull servants will have around 3000 atk. Give him Opti-Camouflage Armor, then atk your opponent directly. Under the protection of stall spells and traps, this strategy will work.

6. Toss: Have lots of cards that will force your opponent to discard cards in his/her hand in the graveyard (The jar monsters will be your main atk force). Boring strategy, and will not work with someone who has 80 cards or if you're tag dueling.

7. Low Stars force: Works if you dont use Messenger of peace. Basically, use cards like Injection Fairy Lily, Opti-Camouflage, and Gyaku-Gire Panda. Have Swarms of Scarabs and Swarm of Locusts to clear out the field before you atk. Also use some atk increasing equip spells traps that will negate the activation of other traps.
You can also use similar strategy with Messenger of Peace and Yubel, but I dont think it works too well.

**Originally, I made these decks out of the hatred for Mirror Force and Widespread Ruin. I have stumbled upon a pretty interesting aspect of the game :).
My burn deck is the one I like most, since I rarely lose with it.

Your worse enemy would be cards that will negate the effect of spells and traps like Jinzo and certain bird monsters. Try your best to remove them off the field while doing business. They should not pose much trouble though, because you have swarm of scarabs and other monster control cards as well.

Why Don't You Try The Elemental Heroes Deck, Its Pretty Cool.
Then Add some more synchrom monsters then special summon Startdust Dragon.!! :))

Well, as for me i didn't lose with this deck, it depends on deck destruction that can make you win from the firsr turn, for example:
try using 3of exchange of the spirit,3 card trooper, 3 cathdrael of nobles, 3 pot of greed, 3 graceful charity, 3 reckless greed, 3 philosifer's stone sabatier, 3 cyber jar, 3 morphing jar, 3 mirror force, 3 magic cylender, 3 painful choice, 3 sixth sense, and 3 card destruction.
The easier will be to you is to be 1st to go, so you can beat your oppenent in the first turn.
to win with this deck you should draw as much as you can and throwing cards in your graveyard, by sixth sense or graceful charity or painful choice, and if you got the philosefer's stone, take cathdrael of nobles and keep drawing until you get exchange of the spirit and use it, and you will see that your oppenent have no cards in his deck so use card destruction , and you will see all of your oppenent's deck in his graveyard and you will win in your turn, and i think that this the best deck plan.

Try the Gladiator Beasts deck.

BEST deck for you to use :

i usually use a d-zombie diva deck or some lightsworn hybrid build , dragons works good very well , and gadget oppression

Hardest duelist :
Luna
a deck of Mina Simington
Naomi
Disa
Hana
Yuma

I'm using gemini monsters and surprisingly, after days on tuning i actually use gemini deck to wipe out almost every character in the game.

I love the sunday tournament which when i tag with yusei i can win 7-8 in a row to get 30k dp =)

The best decks is the deck that you think good
examples: I likes dark deck, but My friend likes lightsworn deck
It's up to you, you can try many decks and choose that fit to you :)

I always win using elemental hero deck

I use Elemental hero deck with some synchrom monsters for example stardust dragon or though ruler archfiend

Yeah, burn deck is good but has it's weaknesses if u cant draw binding cards. and cards like spirit reaper is useless against piercing attacks. however, if u know who u r gonna battle and what they use, u can twitch your deck a little.eg, throw in 3 end of witchcraft if u r going 2 fight a spellcaster user. do this against yr friend. just sometimes ask them about their deck and jot down everything. there is no 1 deck that is perfect and grants u 100% victory. sometimes, it's up to yr favourism

My opinion is Exodia with FULL of normal monster is the best. recipe:
5 parts of Exodia
3 Heart of Underdog
any NORMAL MONSTER you like
*source: yugioh.wikia.com*
add sangan if you want. and my sugestion have 50% def monster 50% atk monster. just have low lv monster and about 5-7 high lv. *include some tuner so you have plan B, synchro*
if you can have the HoU in the first turn, *at maximum* 6-7 turn you'll win. *except if you're dueling some deck destruction deck or hand destruction deck.
best tag partner: terence *as he use HoU too*

hardest duelis in my opinion:
Anca
Naomi
security *Lionel is the Hardest for me*
naturia deck *forget who*

Try Bright's decks. It's pretty cool defeating your opponents with ease.

Frognarchs are boss that is all.