We think you can figure this one out yourself... but your less intelligent friends will find the "Rays Cast" shirt to be highly dangerous. After all, billions of tiny particles (or are they waves) traveling three hundred thousand times faster than a bullet and penetrating every visible orifice of your body just can't be good (unless you have neo-like abilities within the matrix)...
Baffle your friends with interesting facts about your new shirt:
The rays cast from this shirt never slow down. Whether you are one foot from the shirt or a million miles.
Your shirt only runs out of rays when in absolute darkness. (Unless you want to count the non-visible spectrum at temperatures greater than absolute zero, but that would make it less funny!)
If aliens could view your shirt with a powerful telescope from Alpha Centauri, they would actually see it as it existed four years into the relative past. Which would be four years into your future from the moment the rays from your t-shirt were cast.
100% cotton, black, heavyweight t-shirt with warning symbols printed in yellow and red with "Rays cast from this shirt travel at over 670,000,000 MPH" warning printed on the front in black and white. Be afraid, be very afraid.