Cosimo talks about GtkPopover and GtkMenu, but those just sort of have me stunned. Why should I use one instead of the other? We have GtkMenuButton, GtkMenu, GtkModelMenu, GtkModelButton, GtkPopover, GtkPopoverMenu, and they all sort of do the thing. I have no idea which to use nowadays.
(This is not a chance to explain what they do: I have an understanding of what does what after reading the docs. But imagine someone who's never done GTK+ development before. What's the new hot, "correct", widget to use if you want a menu button in your app? What's it called? OK. Why are the others there?)