It's really hard to choose a favourite hymn out of so many great ones. Most of mine tend to be Lenten hymns, like My Song is Love Unknown and When I Survey the Wondrous Cross or hymns set to tunes by Bach, Holst and other masters. In the end I plumped for Praise, my Soul, the King of Heaven because it's a happy one. For my hate I picked dreary Lord of the Dance because I think the rot set in when it was introduced. Not that I dislike everything modern: it's banality and poverty of language I object to.
You can vote here.