The technology that gives starships and stations a steady pull towards the deck, generated by gravity plating and so reliable that its rare failures are memorable events.
Artificial gravity is taken for granted on nearly every ship in Star Trek, from Enterprise NX-01 to the far future. Gravity plating built into the decks produces a field that holds the crew down, and it usually keeps working even when main power has failed.
Star Trek: Enterprise shows its limits. In Broken Bow, Travis Mayweather relaxes in a sweet spot on the NX-01 where the field reverses, and in other episodes a faulty system leaves Captain Archer floating in his shower.
The best-known failure comes in Star Trek VI: The Undiscovered Country, when a torpedo strike knocks out the gravity on Chancellor Gorkon's ship Kronos One. Assassins in magnetic boots walk through the helpless Klingon crew and shoot the Chancellor.