Fuel jettison in Top Gun, is there any reason to do this other than show-boating?
Doesn't look like it was any 'tactical' reason- rather it was used to get a cool shot, which is totally OK with me. From rulit.me:


  While setting up for a filming pass, the camera crew had difficulty spotting the gray F-14 against the mountainous background. Over the radio, Rat asked the pilot to blip the fuel dump switch and make a mini-cloud. The resulting effect of the atomized fuel swirling in the Tomcat’s vortices looked so good that this technique was used several times in the finished film.


I think they're talking about this scene:



Image from youtube screenshot

Looks like they used this technique to frame the aircraft against featureless mountains, sky etc.

Note: The site seems to have taken the quote from Topgun Days: Dogfighting, Cheating Death, and Hollywood Glory as One of America's Best Fighter Jocks by Dave Baranek.