Wow, there's no WAY I could pick one. There are at least a handful that have a super-special place in my heart, and then a bunch I just think are awesome.
Herbie: I remember watching The Love Bug and Herbie Goes to Monte Carlo at LEAST once a day when I was little. I even didn't hate Herbie Fully Loaded.
Figment: Old school of course. He just kind of summed up how awesome EPCOT (and WDW to an extent) was to me when I was younger.
Goofy: Total classic, and my favorite of the "big 3"
Stitch: Sure, he's a demonic little ______________ (which is awesome) but deep down, after he's gotten all the murder out of his system, he's a sweet kid that just wants a family.
Tron: He's a microchip gladiator, how pimp is that.
Jack Skellington: Halloween's Santa, which is awesome.
That one goofy owl in Sleeping Beauty: "Hoo hoo hoo!"
Jessica Rabbit:
Captain Jack Sparrow: Savvy?