Batman x Watevra
I gotta say I loved this romance. It wasn't a big focal point, which is understandable but I thought this relationship was cute because it was totally unexpected. Especially with the LBM where many probably figured he'd either eventually get with Barbara or possibly Catwoman down the line.
Though it's not too late. They could be broken up in a future film, but I hope not. I'd like to see more of their ship in another film, or even just some new tv spots.