What a great idea for a panel. I never finished, but I once attempted to make two Merlin vids to Mary Chapin Carpenter's "I Take My Chances"--the original radio release is a peppy up-tempo ode to fearlessness and really fits the first two seasons, but the acoustic version she released later, in which a few lyrics have changed and you can hear her age and the cost of having taken risks in the song, and yet the singer keeps on taking them, is much more poignant and fits the later seasons. I still think risk-taking is a fascinating topic in that show.

You have a lot of great recommendations here, but I want to add
Glass Coffin by giandujakisss (http://giandujakiss.livejournal.com/?skip=20&tag=my%20vids) for VR.5 &
Waking World by Di Wey (https://www.youtube.com/watch?v=_uuJePU2-Yk) for Morgana & Guinevere in Merlin

They really do use the song to vastly different effects. Generally I find YouTube is a great resource for finding multiple vids & canons set to the same song.

Good luck!