Is this an external cannon on an F-16? What is the black pod starboard of the front landing gear on this F-16-I? At first I thought that it was a laser finder, but upon closer inspection it seems to resemble some type of short cannon. What might it be?
What you seem to have found is the Litening Targeting Pod. 


  Northrop Grumman's widely fielded LITENING system is a combat proven,
  self-contained, multi-sensor targeting and surveillance system.
  LITENING enables aircrews to detect, acquire, auto-track and identify
  targets at extremely long ranges for weapon delivery or nontraditional
  intelligence, surveillance and reconnaissance missions. Source


pod http://media.defenceindustrydaily.com/images/ELEC_LITENING-AT_on_F-16C_lg.jpg

The F16 does have a cannon as well, but it's located on the port side under and aft of the canopy: