Here's a unique idea for a Halloween costume:  a snowflake! 
You could cut out a snowflake pattern from 
some white cardboard, or maybe some foam board, 
leaving a hole for your face. 
Put a strap on it to reach around behind your head, 
to hold the snowflake on your face. 
Wear a white jacket with it,  and go around saying things a snowflake would say, like:
"Your costume offends meee!  You can't wear thaaat!" 
"You hurt my feeeelings!  I need a safe spaaace!" 
"That is so sexissst!" (or racist, or _____ist) (Fill in the blank.) 
"That is so insensitive!  You can't say thaaat!" 
You could mount a GoPro camera on the costume to record people's reactions. 
See how many REAL snowflakes are offended by your snowflake costume! 
Some cities have a block party every year at Halloween, open to the public.  
That would be a great place to try out the costume!