iconoclast
Meaning: one who attacks common beliefs or institutions
Usage: Jane goes to one protest after another, but she seems to be an iconoclast rather than an activist with a progressive agenda.
idiosyncratic
Meaning: peculiar to one person; highly individualized
Usage: Her idiosyncratic note-taking system made perfect sense to her but confused everyone else.
maverick
Meaning: an independent, nonconformist person
Usage: Andreas is a real maverick and always does things his own way.