Ok, so for me it's definetly IchigoxInoue
Why not IchigoxRukia? Because they just awesomly good friends, only FRIENDS. Yes, they have very good relationship, they can talk with each other about everything and they can understand each other without words. But those are very often the signs of good friendship. And also, even if Rukia liked Ichigo a little more than a friend, I think Ichigo couldn't be with her - simply beacus she is a precious firend to him.
Now for the IchigoxInoue
Yes, they are too very good friends, but in this friendship there's something more (yup especially from Inoue side -> ch237
). This pairing has bigger potential(of course in my opinion ^^).
Many of you say that they have different personalities (wheras the personalities of Rukia & Ichigo are nearly the same) - but this is what you need for a good couple: Different personalities NOT the SAME.
When people have different pers. they can fill each other with different emotions, reactions etc, wheras the same pers. will always be fighting with each other.
Ok, so much from me
I hope that my explenation and english isn't too bad