Calvin & Hobbes / Firefly shirts:
http://www.redbubble.com/people/khallion/t-shirts/7863915-malvin-and-cobbes-v2
http://www.redbubble.com/people/khallion/t-shirts/7726932-shiny
http://www.redbubble.com/people/khallion/t-shirts/7046894-malvin-and-cobbes