Small little c programs that can make "music" (really just repetitive noises). Pretty neat.
IF YOU ARE ON LINUX, TRY THESE:
echo "main(i){for(i=0;;i++)putchar(((i*i>>8&46&i>>8))^i&i>>13);}" | gcc -x c - && ./a.out | aplay
echo "main(i){for(i=0;;i++)putchar(((i*i>>8&46&i>>8))^i&i>>13);}" | gcc -x c - && ./a.out | aplay