Let's see...
:cc: The Orca, it rocked for bombing runs.
I didn't really care for the game, but the Wolverine or Hover MRLS.
The Flame Tank. I love how much damage it gives out and can take. One of the mainstays in my attacking forces. That, and the Stealth Tank, looks awesome as it slithers around the battlefield. And it actually does adequate damage WHILE having a great special effect.
I'm not really a fan of GDI, but I am now. The Hammerhead Gunship. With AP Ammo upgrade and a few Missile Squads, they shred up anything.