shuf -n 1 <<< $'H\nT'

shuffle two lines of Bash Here Strings, using C-style string $'' to have the escaped the newline, for one random line, that is either “H” or “T.” You can certainly use echo -ne to achieve the same things, but Here Strings is simpler in my opinion, I seem to prefer using it more.

21 characters, that’s as short as I can manage. Or do you prefer to play Russian Roulette with your life or computer?