I came across this interactive infographic last weekend, which shows the vocal ranges (along with examples) of some of pop and rock music's most notable vocalists. The chart bases the ranges on recordings of each artists, selecting songs showcasing their lowest and highest notes of all their recordings.
Of course, the chart does not show all artists, it focuses on some of the more popular singers over the past half-century. It would be interesting to see the same list with a more-inclusive sampling of artists, spanning more genres.
Lowest Note: Guns N' Roses - "There Was a Time"
Highest Note: Mariah Carey - "Emotions"