Well, I'll definitely give this a go, since I used to love Yugioh and still have most of my (very outdated) cards. I watched both the first anime and GX, read the slightly different original manga, and still own a few games (Dark Duel Stories, Eternal Duelist Soul, Forbbiden Memories, Duelist of Roses, and World Tournament 2006).
I never was very good IRL and never had the money to buy enough of a pack to make a workable deck. In WT 2006 (the closest to real playing), I usually went for what counted as a quick beatdown deck back then (mostly 1900 attack monsters). My favorite character from the anime was somehow Rapheal from the Dragons filler arc......I always liked the Guardian cards, though now I know the only ones worth playing was Eotos (and somewhat Grawrl in WT 2006). Though not an archetype I always liked the cards that connected/was related though connected card-art/story (Impatchi line, Gigobyte's evolving story, the small light and dark faries...., etc). Overall, my favorite card ended up being Chaos Sorcerer for some reason (probably the whole light and dark theme).
Well, that was a bunch of Yugioh rambling to sort through. You know my favorite mon is Gardevoir, and I made my title 'Mecha lover' for a reason. Is there any other info I need to add?