Sperm Whale [2] (Physeter macrocephalus) regular clicks. Recordings courtesy of Dr. Peter Tyack and Woods Hole Oceanographic Institution (WHOI [3]).
Links:
[1] http://csi.whoi.edu/audio/spermwhale-audio-III
[2] http://en.wikipedia.org/wiki/Sperm_whale
[3] http://www.whoi.edu