Tam and Brigid have weighed in on opposite sides of why they will or won't name things.
For me, I take a third road. While Brigid is very right that to name something is to claim something, to make it theirs, to name something is also to give it an existence separate from the mere fact of itself, to give it a story.
There are many cats, but there will always and only be one Mouse Patrol for me, with his raging defiance at the redtail hawks that would steal his prey, his bloody smug pride at defeating river rats, and his utter contentment in sleeping on top of the air compressor or the welding bench, startling the hapless welder who didn't realize the utter feline indifference to noise and sparks less than two feet away. He passed away quietly in his sleep almost two decades ago, but still he lives on in stories.
Stories are powerful things, breathing life into the inanimate, bringing meaning and pride and love and luck to memories, hopes, and dreams. The best stories outlast both their makers and the things which they relate - to name something, therefore, is to give it an immortality that the unnamed tool next to it will never have. And once so named, a thing often takes on the personality and gender seen in the owner's relation with it - for it becomes a character all its own, and english has no respect for a neutral gender.
I did not name my plane; she came to me already named, with a tale of the trials of her engine and the places she would go, the mishaps she has been through, the triumph achieved in her. Her prior owner, as he was telling me the story of their time together, was deep in technical details when he paused, and in a soft voice, told me her name. My IA has worked on her for two owners before me, and one day a man came in to see who owned her now. He was a little uncertain on my name, but he asked for the plane's owner by her name, and told me that if I could get her back in the air, it just might make him cry.
To name a plane is to love it.
There is this, as well: An owner of a P51 Mustang once noted that after a certain point, you are no longer the owner of a plane - you are the caretaker of an irreplaceable piece of history. While he was speaking of a beautiful fighter that makes young boys excited by the very sound of her engines, and old men who once flew her smile very quietly as they are helped into the cockpit and realize that they still can find every control, and their hands and bodies remember all the flows - mine is a much more humble machine, pressed into service after Pearl Harbor to train young soldiers who might have then gone on to fly fighters like his. Still, he has a valid point, and all the hopes, dreams, fears, and joys of the men and women who have encountered her have left her with a story as complex as the inner structure of her wings.