Perpetually-Shiny Bodies

In a lot of animated shows and comic books, characters that are supposed to have particularly "tight" bodies will be depicted as having a constant high-gloss on their exposed skin, even when they're supposed to be completely dry. This could be to emphasize their muscle tone, or to draw more attention to a woman's bosom or legs. If done well, it will give the impression of youthful elasticity and sturdiness. If overdone, it might lead to characters looking more like inflatable dolls, which might or might not be the the desired effect.

Examples of Perpetually-Shiny Bodies include:

Ikki Tousen
Rio -Rainbow Gate!-
Queen's Blade
Dead or Alive
Most DC and Marvel characters have undergone this, depending on the artist. Especially the female ones.
Saki
Parodied in Excel Saga, where in an episode parodying fanservice anime they turn up the contrast and brightness of the show to achieve this effect.
Order of the Stick parodied this in the strip introducing the gladiators.

"You will remain stripped to the waist with your muscles oiled at all times, for no apparent purpose. See the oil steward if your skin becomes dry for any reason."

Many western comics during the Dark Age of Comics utilized or imitated the style of the Liquid! coloring studio, which emphasized heavy use of bright, primary colors and more light sources than a Thomas Kinkade painting.
Masamune Shirow (example pictured at right) became the absolute master of this trope when he started drawing highlights on his characters with Color Dodge layers in Photoshop.
The works of Satoshi Urushihara.
The works of DP Ragan, particularly due to his tendency to go for Dressed All in Rubber as well.
in Real Life, celebrities often rub oil into their skin to achieve this look.