money shot

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Slang A photograph or film sequence of assured commercial value, as for its emotive power or prurient appeal.
• noun Vulgar Slang A sequence in a pornographic film or video that shows the act of climax or ejaculation.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The shot or scene of a film that cost the most to produce, most commonly an action sequence. Alternatively referred to as the 'money-making' shot.
• noun The moment in a pornographic film where the male subject of the scene in question ejaculates; so named because it is often considered the most important part of the film, and often an actor who is unable to provide the shot goes unpaid.
• noun The photographic capture of a willing female proudly displaying her breasts for free, or enticed to raise the shirt for photographing.