Ultimate Ben

Ultimate Ben is the evolved form of Ben Tennyson. His appearance does not change despite evolving, but it enables Ben to use any alien's abilities and powers without needing to change his physical human appearance.

Powers and Abilities
Ultimate Ben would just pronounce the name of any alien he chooses to transform to (though it is not necessary) or press the Ultimatrix symbol on his chest. Ultimate Ben's size changes depending on the size of his chosen alien, as seen where he accessed Ultimate Humungousaur's powers, Ultimate Ben's body frame increased to fit Ultimate Humungousaur's.

Seen briefly, after Ben reverted back from Ultimate Spidermonkey in Fame, Ben's eyes glow pink for a moment. Dwayne hinted that the pink eyes Ben displayed are part of the human ultimate form.

Aliens Accessed as Ultimate Ben (Ben 10,000)
Ben 10,000 said that he has pretty much all of the aliens powers.

Trivia

 * Ultimate Ben 10,000 says that he has not transformed into another alien for years since he discovered Ultimate Ben, the others having become unneeded since he can use all of their abilities as Ultimate Ben.
 * Ben 10,000's attitude is the exact opposite of the original Ben 10,000, who was always in alien form until the episode Ben 10,000.
 * Ultimate Ben being able to gain abilities refers to human adaptability, which is said to be an ability that only humans possess.
 * Ultimate Ben 10,000 said that present Ben will figure out Ultimate Ben's abilities someday.
 * Ultimate Ben is the only Ultimate with no visual changes, except for the Ultimatrix symbol and when using a large alien.
 * When Ben 10,000 goes Ultimate, he doesn't slap the Ultimatrix, he seemingly just twists it clockwise.
 * Ben 10,000's Ultimatrix resembles the Omnitrix from Alien Force.
 * His ability to use alien powers without transforming is similar to Eunice's ability to absorb the powers of other creatures and use them without changing.