The Mobile Suit Gundam Franchise. When it comes to destruction, nothing beats the 18-meter-tall-Battle-Machines-of-Death known as Mobile Suits--save, perhaps, for the Gundams, which are the pinnacle of Mobile Suit Technology.
Of course, I also like The King of Braves GaoGaiGar and The King of Braves GaoGaiGar FINAL--GaoFighGar can cause about as much destruction as some of the most powerful Gundams!!!
Star Wars for me. Since I was a kid, I've always been enamored by adventure, swords, telekinesis, heroic knights and high technology. Star Wars has them all in one form or another, all packaged in an epic space opera of good versus evil. One of the few high-technology sci-fi universes where you can have sword fights and still have an actual reason as to why they exist in such a setting.
A close second for me... the Armored Core universe. Loved the games. And there's just something about being a lone freelance merc that customizes and pilots ones own mech for a living that I really like.