While BB-8 may have been the robot that stole the show during The Force Awakens, C3PO hung in there with some funny one liners, red arm and all.
Here's the few funny quotes he managed to utter.
To Han Solo as he meets him for the first time in a while at Maz's now destroyed Castle:
"Goodness! Han Solo! It is I, C-3PO! You probably do not recognize me because of the red arm..."
C3PO then shows a complete lack of emotional intelligence getting in between Han and Leia having not seen each other for what would appear to be an age:
"General Solo, it is such an honor to see you again."
C-3PO corrects himself in front of General Leia:
"Princess — General, Sorry."
To the long powered down R2-D2:
"Oh dear friend, you don't know how happy I am to see you."
Here's some more classic quotes that C-3PO has made in the other Star Wars films.