The Oto Melara 76 mm naval gun is popular in many navies around the world.  It has a high rate of fire and can be used for anti-aircraft, anti-surface and ground shelling.  It is compact enough to fit on small warships.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/37804160@N00">Mike</a> from Vancouver, Canada
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/37804160@N00/1702023083/">HMAS Sydney #03</a>