I'd consider R2D2 and C3P0 characters - they possess distinct personalities. At certain times (when required by the story,) the Enterprise computer may even exhibit character-like qualities. But those are supposed to be AI.
The Enterprise itself, though, or the Millennium Falcon, the TARDIS, the Batmobile? I'd have to categorize those as settings, rather than characters. Familiar settings? Sure. Settings we're supposed to feel are important, because of their familiarity and because of their importance to the main characters in their respective stories? Absolutely so - often, they're essentially the place the characters call home. But I'd still call them settings, in the same way that Starfleet Headquarters or Tatooine or London or stately Wayne Manor are settings - they're places where the story happens to (or is made to happen by) the characters.