Take off your one undergarment. Use your finger as a pen and your fecal matter as ink. Draw an x-y coordinate plane on the ground. Now throw your undergarment in the air and note which direction the elastic (or top) part is facing. Once again re-ink your pen and note this angle (from 0 to 360 degrees). Do this as many times as you feel will satisfy randomness. Take the sum of the angles and divide by the number of times you did the experiment (theoretically once should be enough).

To expand on the range do this another set of times, except this time take the sum (no average) and use this as the exponent.

Congratulations, you have successfully generated a random number using only your finger, fecal matter, and a little bit of math.

Now sit in this room of solitude until you die or are released from Guantanamo Bay.