As a hobby, I like to come up with deck ideas, and sometimes, I get to test these deck ideas out.  As of right now, I only have money to work on a deck for tournaments(it's beatdown as of right now), but I still like to design some decks that could be really good.  I won't add any decklists, but I will throw out the ideas for anyone willing to try and build them.  These are also mostly original, meaning they are either decks I thought of myself or one of my casual dueling buddies came up with.  They are also in no particular order, either.
10. Permission Deck: Anyone who plays Magic recognizes this as a blue deck with a lot of counter spells.  This deck simply says no, and it would include the basic control Spells and Traps like The Forceful Sentry, Imperial Order and Delinquent Duo.
Monsters include Jinzo, Spell Canceller and Tribe Infecting Virus.  My thoughts are that it would include other control cards like Solemn Judgement and the like.  Sideboard for its worst enemy: another Jinzo.
9. Destruction Deck: This type of deck is something my friend used to run for casual dueling for some n00b guy who used a lot of power cards in a 65 card deck.  It had Man-Eater Bugs, Old-Vindictive Magicians, Swarm of Scarabs and Swarm of Locusts and other destruction cards.  Anyone with more money can sub out the commons for stuff like Breaker and Exiled Force.  Note that the idea is to destroy everything that comes into play, not just Monsters or M/T cards.
8. Ritual Deck: I'm trying out a ritual deck for fun, now that I have a Relinquished and Dark Master Zorc to go along with the Black Luster Soldier I already have.  Zorc and Relinquished work best if the Ritual deck is control based.  Add BLS, Shinato and Masked Beast for a beatdown-type deck.
7.Punishment Deck: Another deck from Magic except the concept of this is Red instead of Blue.  The idea is to force your opponent to lose something should he/she try to make a move.  Curse of Darkness, Chain Energy, Toll and others like it are for this deck.
6. Elemental Deck: Restrict cards to those of one of the Four elements: Earth, Fire, Wind and Water.  Also, don't settle for just one type of element, either.  Monsters can include Tribe Infecting Virus, Exiled Force, Sasuke Samurai and a whole host of cards simply Earth, Fire, Wind or Water.  Also, throw in cards like the new Earthquake card, Windstorm of Equata(not sure if spelled right), Ookazi, Torrential Tribute and other S/T cards besides staples with an elemental feel to it.
5.Bad Reaction Deck: I know it's not a good idea to rely on one card, but a fun card to try out is Bad Reaction to Simoochi and various cards that gain the opponent lifepoints.  Cards include Snatch Steal, Upstart Goblin, Rain of Mercy and finally a use for the craptacular Burning Algae.
4. Trample Deck: This deck is full of Trample-based monsters like Dark Driceratops, Spear Dragon and Mad Sword Beast.  Coupled with Equips, this deck can be very strong at beatdown.  You can even add some Trample-giving cards like Fairy Meteor Crush and Meteorain.
3.Life Lockdown: This type of deck can utilize various combos to jack up your life points to a point where doing damage to you doesn't matter anymore.  Most lifegain happens in little increments, but combine some monsters that get really big like Great Maju Garzett, cards like Guardian Angel Joan and Mystic Wok and life gain isn't so slow.  If you want to be cheesy, add the Magical Marionette/Butterfly Dagger/Gearfried combo with Mystic Wok.
2.Soft Lock deck: A soft lock is a lock that is kind of indefinite.  Unlike Yata-Lock, your opponent might be able to break out of it.  However, it won't be easy if you keep forcing your opponent to discard stuff while certain cards keep putting stuff from the field to the hand.  Combine a basic discard strategy with Wall of Illusion, Mystical Knight of Jackal and The Forceful Sentry.  Hopefully, you'll deplete the opponent's hand and continue to draw one monster that the Knight of Jackal will keep killing.
1. Bait Deck: This deck is also known as a donation deck because your opponent will continue to trade his stuff for yours via cards like Invader of the Throne, Creature Swap, Snatch Steal and Exchange.  The idea is to use his/her stuff against you.  This is control-based, so any control type cards you feel like adding is optional.
       Any comments on the decks?  Just send them to me at zeno9d9@aol.com.  If I stole your deck idea, or if you got suggestions on my current Ritual fun deck, let me know something.  Any other comments will also be appreciated.