Watch the Power Chords online guitar lesson by Vicki Genfan from Acoustic Rhythm Survival Guide
TRY THIS! Combine a bunch of the techniques...
Play around with accenting different beats while playing power chords. Do the 'usual' patterns that you'd hear in a rock or blues song, then try different patterns to bring something new.
Try using power chords in a 'folk song' or 'hip hop' song.
Try using them for a second verse or double chorus for a different texture.
Try playing them in a very slow tempo.
Try picking the individual notes – either with your fingers, or a pick...
Try making up melodies that use lots of color tones – you have a lot of options since all you have in your power chords are roots and a fifth.