Torchwood is full of couples...and would-be couples...Ex-couples...Slash couples...Never in a million years (unless we run out of storylines) couples...Pick your favorite.
I like Jack with...everyone! Ianto, Gwen, John, the real Capt. Jack...all good matches for Mr. Harkness.
But, for me, Owen and Tosh take the cake. I've adored them since Countrycide and even though he still doesn't know what the frak he feels for her, I'm rooting for them. Plus, he's already dead so Tosh's curse can't really affect them now