C-3PO and R2-D2 because they have been the most iconic duo in the entire franchise since they have appeared together in almost everything and they have great chemistry and fun humor

I like Anakin Skywalker and Ahsoka Tano, but come on, it is almost no contest.

C-3PO: "We seem to be made to suffer. It's our lot in life."

If you showed a non-Star Wars fan a picture of C-3P0 and R2, they'd instantly recognize them.

A picture of Anakin and Ashoka, on the other hand? Yeah, they'd probably look at you like you're some cringy weird nerd.