Ichigo and Orihime all the way! Rukia and Renji have been destined (unofficially) to be together since childhood in the Rukon, and apart from the initial episodes and the beginning of the Arrancar arc, she has had little to no effect on Ichigo's power levels. Orihime has motivated Ichigo so much in the last few fights, and I think it's almost entirely confirmed that he feels at least something for her. Whether romantic or not is questionable, but I can really see it happening...