People (usually emo/goth kids) who dress weird in order to distinguish themselves or express their identity. These people think that they are each a "beautiful and unique snowflake" (see the movie Fight Club). Believe everyone else are "conformists".
Plural: "Snowstorms" (large amount of Snowflakes in one area).
Jess is wearing one green sock and one pink one, with a blue anime shirt. What a fucking snowflake.