The Shark Mouth

Made famous by the American Volunteer Group, aka the Flying Tigers, in China, the "Shark Toothed Mouth" design is a variety of nose art that first appeared in the First World War.  A variety of countries have employed it, and the effect can be both comical and menacing.

The Americans are almost certainly the dominant users of the design at present:

 A-10 Thunderbolt II "Warthog"

The appeal of the design lies, probably, in the image of the shark as a sleek predator, always staying in motion to survive.  Plus, big teeth are awesome!

Dassault Ouragon flown by the Israeli Air Force

 

 Apache AH-64D Longbow, flown by the United States Army

The use of the shark mouth for helicopters is very popular with American forces, turning up in Viet Nam on Hueys and continuing as above and below.

AH-1 Cobra Gunship

Because f the popularity on helicopters, it is only natural that it should appear on the sides of the new plastic Valkyrie gunships, which are sort of a mix of Huey air cav and attack gunship.

Valkyrie

Though the design is most often utilized in aircraft, I thought it was worth mentioning that Canada Russia* has a slightly different take on the issue.  And, in my opinion, size does matter.

 Canadian Russian Ice Breaker

* Thanks to an unidentified commenter for correcting my national attribution.