Technically, David Bowie's eyes are actually both blue. His left eye just appears darker, because the pupil is enlarged, ever since he got punched in it while still in school. The effect is mesmerizing, though.
My dad has two different colored eyes! But not evenly...ok. It looks like one eye was very light blue and the other was brown but then he slept on one side and the blue melted halfway into the other eye. So his left eye (er, his right, my left looking at him) is clear blue and a little less than half of the other eye (closest to his nose) is also clear blue, but the rest is brown. It looks cool. I think it has shifted, though--I think the brown one used to be more brown with a smaller piece of blue. I could be wrong, though.
I also know a girl with pretty green/hazel eyes and a large freckle on one iris from where the pupil meets the iris to the bottom of the iris. That's pretty cool looking, too.