A Slow Dissolve (2007)

The day Ryan Locke's father was put to rest was the same day he got his new imaginary friend, Ian. Ian and Ryan have grown up together along with Ryan's friend Sophie, who can't see Ian. One day, though, Ian finds out he has to leave Ryan, for good, in one week. Ryan sets out on his last week with Ian preparing himself for his future without his best friend. While Ian has a list of tasks to accomplish before he will vanish for good.