10. "Geronimo!"
Every Doctor has had their own catchphrase or something they said often enough that it would become associated just with that Doctor. For the Ninth, it was "fantastic." For Tenth, his was both "brilliant" and "allons-y." Eleven also had two phrases he said quite often: "____ are cool" (we'll have more on that later) and "Geronimo." We first saw him yell out this battle cry when he had just regenerated into his eleventh form. After making sure his new body was in order, he realized that the TARDIS was on fire and crashing down to Earth. Rather than freak out like most of us probably would, he grabs the control console, holds on for dear life, and shouts "Geronimo!" while plummeting down. After that, he commonly said the phrase when diving into a new situation, whether it was diving into the overturned TARDIS to begin repairs or getting ready to face down a sky fish who ate part of his sonic screwdriver. In one sense, he sent the word as the last written message in the universe to Amy, Rory and River before he rebooted the universe in The Big Bang. Even Craig, his two-time companion, said the word before touching the alien console that was causing all the ruckus in his building. I have to say, as a word to say when your about to do any thing unexpected or exciting, it's a pretty good word.