Hmm, I remember when I was little I always wanted to be The Dark Magician, and then when I got Yugi's deck with the Dark Magician, I Treasured it!....and then it got thrown away ._. So yeah, DM.
Favourite monster huh.... When I first started Yu-Gi-Oh and watched the anime, I liked Red Eyes Black Dragon, plus, Red Eyes is stated in Season Zero's movie to bring out potenial while Blue Eyes brings victory as this is true as Red Eyes can fuse with Meteor Dragon or Summoned Skull to beat BEWD in Attack power. GX Series did have Red Eyes so once again, my favourite. 5Ds is Stardust Dragon since it can negate destorying cards and revive itself with a built-in Monster Reborn but now that Season 3 is ongoing, it's Stardust/Shooting Star Dragon.
Crystal Beast Topaz Tiger or Winged Kuriboh LV 9. For no specific reason i can think of, and definately not because they helped me.
I always liked Dark Magicians when I used to play a lot, my deck still has three of them in there, haha. I really wanted a Dark Magician Girl, too. :c I do have a Skilled Dark Magician, which is an awesome card.
Dark Eradicator Warlock. T'was my trump card. I only ever used it a few times and it never failed in an actual game. Second to it was my original Dark Magician, I received a second Dark Magician I called DM3 with the DEW though, I called it this since a friend of mine had a Dark Magician with a different picture already which was DM2.
Black Luster Soldier. Not because if I ever get it I'll PWN my friend with it....oh no, that would be...cruel.
My favorite cards would have to be the Red-Eyes series. I kinda like the Six Samurai, though. But my trump card (before I lost my deck. :c) was definitely Time Wizard.
I don't really see what's so threatening unless you're talking about the one that's Banned/Forbidden...