LA's Secret Headquarters (best comic shop in town!) has a limited supply of t-shirts based on Brian Wood's wonderful DMZ comics. They bear a sterling Wood illustration on the outside, but can be reversed to reveal the word "PRESS" screened in white on the inside, for those moments when you want to be identified as a non-combatant.
(Photo of me modelling tee by Greg Ehler)
Update:
Corey sends in this Barkeater Lake comic he drew as a Brian Wood tribute.