Congratulations to Heather who correctly identified this organism! This is indeed Trichomonas hominis; a non-pathogenic flagellate from a stool specimen. It has now been renamed as Pentatrichomonas hominis.
Here is her description which I include because it so perfectly describes the motion of the Trichomonads:
Go and watch the youtube video (you don't have to watch the whole thing - just the first 5 seconds and you'll get the idea), and then check out the following. Alex from Rip and Read (also my husband) made this for me. Fun!