i say Rainie and Xiao Gui..
Genie & Xiao Gui: they did a duet before already
Hu Die & Xiao Gui: they hosts YLBFB together sometimes
Rainie & Xiao Gui: although they "collaborated" in real life before but we didn't get to see that.. so i'd love to see them do a duet or film a movie/tv series together or a tv commercial will do for me.