I love rock ballads. Can't say i'd use them as workout material, but whatever floats your boat. Here are some favorites off the top of my head:
"Goodbye", Night Ranger
"Home Sweet Home", Motley Crue
"Heaven", Warrant
"Ballad of Jane", L.A. Guns
"House of Pain", Faster Pussycat
"I Remember You", Skid Row
basically anything by Bon Jovi
"I'll Never Let You Go", Steelheart
"Love of a Lifetime", Firehouse
Christ, thats enough. I'm starting to embarrass myself here.