RE: Your favorite deck
Regigigas LV.X, plus various decks and side attackers to go with it. Dubbed "RegiAwesome" by me, its contents can only make people stand back in awe and watch at how amazing the deck is (most of the cards in the deck have only 1 copy of that card in). It was something I started running when Rising Rivals came out, but it reached its pinnacle performance during the MD-on era. To this day, I keep maintaining the decklist as an MD-CoL, finding new ways to perfect it. And, ironically, I've only revised it ONCE since the rotation - it goes to show how comfortable I was with the deck and how well it performed. (That, and there's no such thing as a skeleton Regigigas list - it is always tweaked and refined to suit the user's needs.)
It almost got me into what would have been my first topcut (Long Beach Regionals Spring 2011), and I only barely lost out on it. For anyone who's seen my deck in action...you'll know it when you see it.
All Hail Gigas!!