I said Matterhorn!
When I was little I saw it on the back of a cereal box, and so on my first trip to Disney at age 5 I spent the whole trip looking for it, only for my parents to tell me it was in California! I finally went to SoCal to visit a friend over the holidays in 2009-2010, and long story short she abandoned me at the
Disneyland gates on my last day (I cut the trip a week short bc of her, but that's another story!). Come heck or high water I was determined to get my tush on that ride, especially after seeing it from the highway for a week! I got a toboggan all to myself, strapped myself and my purse in, and off I went! I screamed and laughed my head off and had tears running down my face from the wind! I may have even tried to yodel a bit...

It was a blast, and so worth it.
I know WDW already has quite a few Mountains, but the old Matterhorn is special to me!
I wanted to vote for
other as well, for DL's PotC. As much as I love "ours" in WDW, the one in DL is amazing! I love the double drops and the bayou in the beginning. But the Matterhorn is obviously my baby!