Watch the The vi-V-IV online guitar lesson by Ravi from Guitar Lab: 30 Rock & Pop Progressions
Again, we are really suggesting the very common I-V-IV, but by substituting the I with its relative minor (vi), we get a darker sounding progression with the vi-V-IV. Some may argue that this is really a progression based in a minor key since it is grounded on the minor chord that it starts with. While it is an acceptable interpretation, it introduces a new layer of analyzing progressions in the context of minor keys. Since minor keys share the exact same notes as their relative major keys, it really isn't necessary in order to understand and apply these chords. In fact, it adds to the amount of theory you must memorize without yielding any real benefit.
What is nice about starting with the vi and going to the V and IV is that it automatically descends in the bass without having to modify any chords from their most common voicings. Emphasize the bass notes, especially when the chord progression is being used for that purpose. Don't be afraid to lay into the strumming a little harder when you are playing a harder rock song.
Examples: Under My Thumb, All Along the Watchtower, Dream On, Stop In The Name of Love