Little Pete in the Gone series. Normal kids powers rank from 1-4, with Sam and Caine being the only two fours. Little Pete is rated at ten, considering he has the ability to create monsters and levitate things out of nothingness in Hunger.
A character in Sewer, Gas & Electric goes Up to Eleven in both lavish extravagance and in attempts to impress one's date with one's wealth, investing $10,000 in a top-of-the-line pack of condoms.
Dune Messiah: Alia Atreides engages in a sparring match with a mechanical swordsman, which gets faster, and creates more lights (which reflect off its prismatic body to distract its opponent) every time it is struck. It's noted that the greatest swordsmen in the universe can strike it seven times before it becomes too fast to safely continue. Alia manages to strike it eleven times, before Paul stops her. (This book was published in 1969, which makes Up To Eleven Older Than They Think.) And he does it by throwing his knife, striking a one millimetre diameter switch. What makes this even more impressive (up to twelve, anyone?) is that the mechanism is protected by a shield whose resistance varies directly as the speed of the impacting object - more than about nine centimetres per second and the thing won't penetrate at all.
Matthew Reilly bypasses eleven in his books and goes straight to sixteen. One example: the heroes are in a truck and being chased in a tunnel barely wide enough to hold a car. The solution to get rid of the bad guys? Call in a plane, have it fire a missile down the tunnel, and drive the truck hard against the wall so that the wheels on one side ride up the wall, allowing the missile to shoot below the truck and kill the bad guys. This is one of the less extreme examples.
The Star Wars Expanded Universe is full of much "up to eleven" material, including a tiny ship which has a power factor that makes the Death Star itself seem like a cap gun, a Sith Lord who sliced through a planet with his lightsaber, and combat movements that seem to be too fast for the human eye to collect (Thank God they're written down, then, eh?)
Luke's powers have been taken Up To Eleven, especially by Troy Denning. (Matt Stover, however, has Luke see the heat death of the universe. Seriously.) Kyle is too; he actually survives being stabbed through the heart with a lightsaber. It actually goes back to Bantam, when Zahn made a big deal about Luke's powers being taken Up To Eleven. He didn't exactly win that battle.
In The Dresden Files, during the Finale of Changes, this trope is invoked by the narrator when he describes Molly, his apprentice, ramping the battle's chaos Up to Eleven with what he calls her One Woman Rave spell. Thomas goes into Dance Battler mode in response with a falcata and an automatic.
The gamebook for the RPG takes this trope...well, one step further. The book describes evil wizards as having arrogance turned Up to Eleven, and Harry's margin notes remark that it should be thirteen. This is followed by Will and Harry re-creating the Spinal Tap scene with altered dialog.
The children's book Green Eggs and Ham was written as the result of a friendly bet: Dr. Seuss's publisher was impressed that The Cat in the Hat was written using fewer than 300 different words, and bet Seuss that he couldn't write another one with a coherent plot using only 50 different words. Seuss hit it right on target.
Sir Terry Pratchett explicitly invokes this trope on the Discworld. He said of his portrayal of an Ancient Egypt-alike civilization that this is Egypt with all the knobs turned up to eleven. He also described the Assassins' Guild School as a typical British boarding school with all the knobs - including and especially the one marked "violence" - turned up to eleven. "Up to eleven" also describes his parodies of various nation states of Earth: these are so over the top as to be caricatures. XXXX = Australia; Quirm = France; Brindisi = Italy; Llamedos = Wales; Uberwald = Bavaria/Switzerland, and so on.
Agatha H. and the Voice of the Castle (a Girl Genius novel): Sparks cause a deep and instinctual fear/loyalty in non-Sparks, especially when they are fully within the Madness Place. Sparks, however, are excited or even aroused by this behavior. When Agatha drinks the Dyne water and begins to ascend, every other Spark in the room tries to run for their lives.
In Dinotopia Sunstones are said to have a Moh's Hardness of 11. A scale that IRL only goes up to 10 (diamond).