I have never officially named a vehicle. I am very sentimental about my rides though and sometimes refer to them with nicknames...
My 83 Firebird - Bird of Prey
Titanium ZX6R - Silver Bullet
My old 69 Nova - "The Hulk" (it was green and had a big block 454 engine)
OUr Trailblazer EXT - APC (armored personnel carrier) or "Huey" after the Vietnam era helicopter
Others my family has owned get referred to by their color, Ole Blue, Little Brownie, greenie, ect.