Just list the songs that have your favorite key signature change and your favorite key to listen to! Here's mine:
Dream Theater - Disappear (the climax)
Pain of Salvation - A Trace of Blood (The contrast between the happy intro and the verses)
Seventh Wonder - Alley Cat (Prechorus to chorus)
Symphony X - Set the World on Fire (the intro riff being played in a different key)
Symphony X - Egypt (preverse section is played in two completely different keys and lead to the verse which is in the same key)
I'll look for some more, but those songs are what came up to my mind with key signatures changes that either fit the song or are interesting.
Also, I find Ab minor to sound awesome!