I've alway wondered if he can use a yellow ring,I read once he can't use the green one because his will power is driven by fear,so I always wondered if he would make an excellent yellow lantern
@superguy1591: I wouldn't say he is afraid of a lot, but what does haunt him and holds him back from fully being able to use a green lantern ring is his parents' murder. He isn't willing to let it go because it is a part of him and makes him who he is.
I think Bruce would make a great yellow lantern bur I don't think he's submit to someone like Sinestro which I assume he'd have to do. I'm not sure how evil Sinestro currently is but I'm sure he's at least too much on the anti side of anti-hero for Bruce's taste.
What would be really cool would be if Bruce overthrew Sinestro and rebuilt tge yellow lantern corps in his name. Possibly handing the Batman title back to Dick Grayson while he takes on his new role.