Clowns, cops, and Wall Street bulls: excellent group costume.
Props are good, too. Golden skeleton + hard hat = Dow Chemical Rep.
Why not dress up as a Radical Matador?
Shave your head, and you become an Exxon Executive. DONE.
Classic identity correction: all you need is a $15 thrift-store suit.
¡Celebre el Día de los Muertos con Supervibolas!
Become a mop, then clean up a bank. http://www.yeslab.org/dada
Your Ghillie costume can double as a mop for hurricane clean up.
Don matching costumes in front of an official-looking backdrop, and you have an instant press conference.
If you're going to prank a huge oil company, stay classy: wear all black to be a #shellfail Widow, or rock your best tux as the Master of Ceremonies.