I was banging around on the guitar tonight while flipping through my music collection on my music server, thinking of some stuff to play with some buddies. I came across "Wishing Well" by Free, which is such a great classic rock song. Big riff and just awesome Paul Rodgers vocals (maybe the best voice in all of rock music). Sure enough, key change in the last chorus!
https://www.youtube.com/watch?v=z2Bw_HH_T4g