The rarest character I've ever met was Brer Rabbit at the Halloween Party a while back.
At the time they weren't so rare but they now are but I have met Clopin (Hunchback), Milo Thatch and Vinnie (Atlantis), Dreamfinger and Figment (when I was VERY little), Prince Caspian and Figment (the walk around character) when I was younger.
I'm glad to see someone else met Caspian too. He was my first crush too and he called me the Princess of Pennsylvania.
I'd LOVE to meet my all time favorite character, Roger Rabbit, but alas, I hear because of disputes with the author of his book, he was retired
Last year, though, my mom emailed WDW and asked if they'd send me an autographed picture from Roger for my birthday. Well, WDW emailed DL and asked if they could help me out since Roger doesn't have pictures at WDW anymore (my mom got a copy of the email so I saw it XD). About a week later, I got an envelope from
Disneyland (I think it was DL Guest Relations) and there inside was a black and white picture of Roger in one of the parks signed "To Katie Love, Roger Rabbit". Closest I'm probably I'm going to get to meeting Roger so it means a lot.